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N_Cook <diverse@tcp.co.uk>: Dec 13 09:36AM Had another go at trying to identify an "LP" sized disc I picked up somewhere. I found this reference http://www.ips.org.uk/audiocompendium/index.php?title=MSS   ""Direct Cut Acetate" a system that used a cellulose acetate medium coated onto an aluminium disc which, though soft enough to cut, was sufficiently hard to withstand playbacks without excessive wear" is exactly this description, acetate film over thick Al disc. It has a small hole on the underside , presumably to drive the disc around and resist the cutting force. Unusually this is marked 50RPM, agreeing with the 120 band strobe ring (uk 50 Hz mains) and you play from the inside to outside, has some ragtime like piano music on it, well one track anyway, seems to be 2 tracks. Dated by rubber stamp and endorsing ink, 11 Dec 1944 and AY 1, may have had another letter beforethe A. There isa letter D impressed in the aluminium on the underside near the drive dog hole. I must get around to taking a recording off this disc by modding a vinyl record deck to play it properly. Did the BBC modify their ones to 50 rpm?

adrian@poppyrecords.invalid.invalid (Adrian Tuddenham): Dec 13 11:18AM > I must get around to taking a recording off this disc by modding a vinyl > record deck to play it properly. > Did the BBC modify their ones to 50 rpm?   The Marguerite lathe offered 60 rpm as an alternative to 78. I have never heard of one running at 50 rpm. The strobe was sometimes marked "50 c/s", but the disc ran at 60. rpm.   Yes , the BBC did use 60 rpm for a while, but no disc from this era will have been recorded with the RIAA characteristic, so you will need specialist equipment for correct playback (initially try a Blumlein 300c/s characteristic, it suits most UK recordings of that era). More info on this wil be found at:   <http://www.bl.uk/reshelp/findhelprestype/sound/anaudio/analoguesoundres toration.pdf>   There was a later BBC characteristic known as the "D" system, but this did not come into use until 1949 (so the "D" stamped in the disc is unlikely to refer to this).   You will not get many plays before the quality begins to deteriorate, so make sure you have everything in place before you let a styus touch the surface, so you stand the best chance of getting a good transfer straight away. If the nitrate surface has deteriorated, there are ways of improving it by replacing the missing plasticiser molecules with other chemicals. (If the surface is mud-cracked or there is red powder on it, the disc will be in a dangerous condition and you need to seek specialist help to avoid starting a disastrous fire.)   Generally a 0.0028" stylus is about the right size, but if the nitrate has shrunk, you might need to try a range of sizes to get the best results - or to avoid 'bottoming' on the aluminium if the bottom of the groove has split. Deep spiral scratches are a nightmare because they drag the stylus across the grooves; there are a whole range of techniques for dealing with that situation, ranging from tiltng the deck or playing the disc backwards, to re-cutting the grooves by hand under a microscope.   There is some info about MSS in "Audio Biographies" by Briggs and I believe Cecil Watts's wife published a biography of the firm, although I have never seen a copy.   If you want more help with this, please contact me (I live in the UK).     -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk

N_Cook <diverse@tcp.co.uk>: Dec 13 12:32PM On 13/12/2015 11:18, Adrian Tuddenham wrote: > believe Cecil Watts's wife published a biography of the firm, although I > have never seen a copy.   > If you want more help with this, please contact me (I live in the UK).   wow, what a lot of info that pdf would seem to be now on http://www.bl.uk/britishlibrary/~/media/subjects%20images/sound/analoguesoundrestoration.pdf not read it yet. I'll take a pic of the label and also the reverse with spindle hole and the drive dog hole. Label says "SPEED 50 R.P.M" At the moment I was only trying to think how to fudge a deck to play it. Hang the motor upside down and a 50/45 scaled from the 45 pulley,replacement pulley, if I can find one. I seem to remember not only inside to outside but counterclockwse rotation. Hopefully minimum stylus pressure No idea about antiskating and handedness of the arm at the moment. May end up replaying in reverse and then electronically reversing it. No intention of even applying distilled water to the surface for the moment.

N_Cook <diverse@tcp.co.uk>: Dec 13 01:37PM 3 pics of this disc http://www.diverse.4mg.com/marguerite1.jpg http://www.diverse.4mg.com/marguerite2.jpg http://www.diverse.4mg.com/marguerite3.jpg the third is the reverse, the label on the front is covering over the drive dog hole, viewed from the rear. The tearing around the spindle hole is the only obvious failing of the film, clumsy positioning over a spindle in antiquity? Film laid down like silicone slivers and resist etc in chippery production? spun at high speed with a dot of liquid on the disc? The colours are about right, plum-brown in flat light and coppery tone with slanting light reflecting off the aluminium. The apparent grooves on the rear is probably machining marks of the Al blank. Perhaps the 50rpm business was a "pirated" manufacturer trying to escape patent infringement, I suppose patent library is one route to look into. I'll check again , but the blank space between 2 tracks, with continuation groove, spirals in such a fashion that playing from sinside to out , the disc would be spinning normal clockwise , so hopefully normal handedness of the tonearm and normal antiskating weight.

"Gareth Magennis" <sound.service@btconnect.com>: Dec 13 01:55PM "N_Cook" wrote in message news:n4js67$cli$1@dont-email.me...   3 pics of this disc http://www.diverse.4mg.com/marguerite1.jpg http://www.diverse.4mg.com/marguerite2.jpg http://www.diverse.4mg.com/marguerite3.jpg the third is the reverse, the label on the front is covering over the drive dog hole, viewed from the rear. The tearing around the spindle hole is the only obvious failing of the film, clumsy positioning over a spindle in antiquity? Film laid down like silicone slivers and resist etc in chippery production? spun at high speed with a dot of liquid on the disc? The colours are about right, plum-brown in flat light and coppery tone with slanting light reflecting off the aluminium. The apparent grooves on the rear is probably machining marks of the Al blank. Perhaps the 50rpm business was a "pirated" manufacturer trying to escape patent infringement, I suppose patent library is one route to look into. I'll check again , but the blank space between 2 tracks, with continuation groove, spirals in such a fashion that playing from sinside to out , the disc would be spinning normal clockwise , so hopefully normal handedness of the tonearm and normal antiskating weight.         You might only get one shot at playing this disc, it may be destroyed by that process, as has been suggested.   This may not be your world, but I would take Adrians advice and try and take a digital recording via a normal turntable at 45rpm, if the handedness and anti skate should work the same. Speed/EQ adjustments and even reversing the audio can be done later, much more safely, in software.     Cheers,     Gareth.

adrian@poppyrecords.invalid.invalid (Adrian Tuddenham): Dec 13 02:43PM > http://www.diverse.4mg.com/marguerite1.jpg > http://www.diverse.4mg.com/marguerite2.jpg > http://www.diverse.4mg.com/marguerite3.jpg   Typical centre-start transcription disc of the period. Broadcasters sometimes used centre-start to make sure the louder climax of a performance was recorded at the highest surface speed to give best quality.   Common practice for continuous programmes lasting longer than one disc side was to use two recording machines (often with a single common amplifier). Sometimes thesae were set up so that one recorded outside-in and the other inside-out, this meant that the changeover on playback was less noticeable because the surface noise didn't suddenly change its quality. This system was not popular with the playback operators, who had to check each side carefully and often made mistakes.   The label suggest that there is no question that the intended playing speed was 50 RPM - but it is definitely non-standard.   To vary the speed without a lot of butchery, connect the turntable motor through a step-up auto-transformer to the 100v output of a large P.A. amplifier. Feed the amplifier from an audio signal generator and adjust the frequency to get the required speed change. Carefully monitor the motor current and adjust the amplifier gain so that it is maintained at a similar value to the normal 50c/s current, otherwise you will burn out the motor at low frequencies.   Alternatively, look out for a secondhand Lenco turntable with infinitely variable speed.     > The tearing around the spindle hole is the only obvious failing of the > film, clumsy positioning over a spindle in antiquity?   No, these discs weren't played many times, so it is more likely to be caused by shrinkage of the laquer film pulling away at the centre. It also appears to have delaminated at the rim for the same reason.   > Film laid down like silicone slivers and resist etc in chippery > production? spun at high speed with a dot of liquid on the disc?   ...or edge dipped into a bath of laquer whilst rotating slowly. Both techniques were used.   > The colours are about right, plum-brown in flat light and coppery tone > with slanting light reflecting off the aluminium. The apparent grooves > on the rear is probably machining marks of the Al blank.   They weren't usually machined, the blanks were stamped out of sheet aluminium. Without examining this one closely, I wouldn't like to guess at what caused that.     > Perhaps the 50rpm business was a "pirated" manufacturer trying to escape > patent infringement, I suppose patent library is one route to look into.   No chance, hardly anybody but the BBC and GPO could get hold of MSS blanks during the war; the GPO ran the factory. By 1944 aluminium was in very short supply, so private recordings, when they could be made at all, were being made on glass and even galvanised iron blanks (they were heavy!). The BBC monitoring services recorded onto wax cylinders.   > continuation groove, spirals in such a fashion that playing from sinside > to out , the disc would be spinning normal clockwise , so hopefully > normal handedness of the tonearm and normal antiskating weight.   A centre-start disc still rotates in the conventional direction, it is one of the few conventions in the recording world that never seemed to be flouted. The only time you would need a reversing turntable is if you needed to play it backwards to recover a lost turn because of a jumped groove.     -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk

N_Cook <diverse@tcp.co.uk>: Dec 13 03:33PM On 13/12/2015 14:43, Adrian Tuddenham wrote: > be flouted. The only time you would need a reversing turntable is if > you needed to play it backwards to recover a lost turn because of a > jumped groove.   I think I'll go with the larger pulley, even if not giving exactly 50rpm it will be constant at a measurable speed. The other letter in front of AY 1 may be a J, so JAY 1, a ragtime pianist of 1940s called Jay Something ? The blemish at the rim on the front face is a splodge of powdery paint or tippex, easily removable if/when I dare to clean the disc. No damage on the active face film, a few spots missing on the rear. I'd played it sometime for about 5 seconds, the track stayed intact, played well enough to tell by my nonmusical ears it was a pleasant piece of ragtime piano or some such style of music. I suppose they were double sided discs but only one face recorded on this. But the exposed Al on the rear near the spindle hole does not show machining marks. Perhaps there was an attempt at recording on the rear, but at too low a pressure, it feels smooth to the touch, and the film patterning goes right to the centre. I wonder if the use of Persian blue, endorsing ink (stains well into paper fibres for legal document use) is relevant or that is just the ink pad they had there then. Another recovery program I must get back to sometime is 3 spools of used taperecorder wire that came with a rusted up Magnetophon , circa mid 1950s. one of these https://www.soa.hr/galerija/6/m/1-1_Minijaturni_magnetofon_sa_zicom_b.JPG Hardly anyone could afford one of those pocketsize (well greatcoat pocket) covert recorders, then. It would be unlikely they were erased (unless it was a dismissible conduct if not erased before disposal ) as required the use of batteries only, and no fast erase. 3 batteries to power the peanut valves and motor. I got the motor and mechanics free running again, but ran out of time , before cross-connecting the head to the head wiring of the R/P head of a modern cassette recorder, to hear what,if any, is recorded on the wire.

Jeff Liebermann <jeffl@cruzio.com>: Dec 12 10:50AM -0800 How to operate a tube caddy.   During the early 1970's, I ran a 2way radio service shop. Running it was an accident because no sooner was I hired, everyone else either quit or promoted themselves sideways, leaving me as the sole employee and later as part owner. This condition lasted for a few months of serious overwork, until I was finally able to hire an employee. The shop: <http://802.11junk.com/jeffl/pics/Old%20Repeaters/slides/PMC02.html>   A major part of the operation was maintaining a mountain top radio repeater site: <http://802.11junk.com/jeffl/pics/Old%20Repeaters/slides/Santiago-01.html> When something went wrong, the ritual was to load up the company pickup truck with everything imaginable, drive 12 surface miles to the base of the mountain, drive 16 miles up a windy dirt road to the top, fix something, and repeat the ritual in reverse. 6 to 8 hrs was the typical round trip time.   Replacement tubes were carried in a tube caddy. For those who have never seen a tube caddy, the individual tubes were stored in small personalized cardboard boxes, inside a wooden carrying case like these[1]: <https://www.google.com/search?q=tube+caddy&tbm=isch> My new employee would identify the dead or dying tube, extract a new tube from the tube caddy, insert the new tube into the radio, insert the dead tube into the cardboard box, and replace the box into its place in the tube caddy. Do you see a problem here?   That worked for about 3 months when I discovered that my new employee couldn't seem to fix anything. Various theories were offered, but nothing worked. One day, my employee had a cold, so I had to do the drive up the mountain. Oddly, I also couldn't seem to fix anything either. Then, I noticed that some of the tubes I was using as replacements were obviously ancient and really didn't belong in service. Hmmm...   Upon returning to civilization, I tested almost all the tubes in the tube caddy, and found that well over half were dead[2]. When I mentioned it to my new employee, it took him a while to understand what had happened. I suspected that the thought the tube caddy somehow rejuvenated dead tubes. I resisted the temptation to thrash him about the head, because he was bigger than me. I later found him a job with a competitor.     [1] I still have a tube caddy full of tubes awaiting the demise of semiconductors.   [2] Tube testing algorithm. If the tube tester says it's bad, it's bad. If the tube tester says it's good, it still might be bad.     -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

Jeroni Paul <JERONI.PAUL@terra.es>: Dec 12 12:33PM -0800 > Well I guess it is my turn.   > NAP bigscreen no sound - vertical control IC.   > Everything runs off the data and clock lines. This IC does the "S" correction and things like that pertaining to linearity. It is of course bus addressed. The one line, data or clock, doesn't matter, was clamping the signal down to like 2 volts. Leaky. That meant the data from the EPROM was not read when the unit got initialized so it did not know which sound system it had and never upped that.     I had a similar fault in an Universum CRT TV set. It came with an all white screen sympthom that I traced to the RGB decoder matrix IC holding its RGB outputs to 0V. Replaced the IC, no joy. It was I2C controlled and I even built a simple interface to send commands from the PC, it seemed to ACK fine and all looked right. If not initialized at turn on the raster remained black but as soon as the outputs were activated in any way it would go full white. Finally found the problem: it received a sandcastle signal from the sync processor IC that had the top pulses too low so the RGB IC was not locking on them. The picture improvement IC also connected to this signal had a leaky input and was eating half the signal.

Jeroni Paul <JERONI.PAUL@terra.es>: Dec 12 02:44PM -0800 Chuck wrote: > what the problem was. At his house, the keys didn't work. I spotted > a light dimmer on the wall. Turning it off and the deck worked > perfectly.     I have a SABA music system (radio + cassette + turntable + audio in/out plugs + remote control), time ago I had it connected to a desktop PC to play music from the PC. One day the printer attached to the same PC was taken out for repair due to clogged heads.   The next day I found the SABA turned on with the MUTE activated (the radio was selected so the FM display etc was all lit, but no sound). Since I never used to use the MUTE button and I was the only one at home to use that thing I was quite surprised. I unmuted it and turned it off, all appeared to work correctly. The same day in the evening the same again, that made it obvious it was not me. In the next few days the same kept happening at random times but never when I was there, and because it would turn on with the mute set I could not hear when it happened.   Finally one day it was off, I went to the kitchen and when I came back it was on and muted again, so I guessed a relation had to exist. Turned it off and went to the kitchen again - no joy. Repeated a few times and surprise - again on and muted. Some more experiments revealed that switching off the kitchen light sometimes would cause the SABA to turn on and activate the mute at the same time.   The kitchen light consists of two 36W fluorescent tubes, apparently the inductive kick at turn off found its way into the SABA digital controls. They were two rooms apart, so not exactly next to the kitchen switch or lights. The issue did not reoccur after I plugged the printer back.

Jeroni Paul <JERONI.PAUL@terra.es>: Dec 13 06:53AM -0800 Mark Zacharias wrote:   > Any more recent successs stories to brag about?   > C'mon, don't we all enjoy patting ourselves on the back, really?   > Mark Z.     I was in a block of flats to look at a curious problem in their terrestrial TV reception. Whenever the communal stairs/hall lights were on, all TV sets in the block lost signal. The stairs lights were controlled by a timer relay that kept the lights on for a few minutes after any push button was hit, so every time someone entered and hit the light the neighbors TV signal went out for a few minutes.   I started checking the terrestrial antenna head amplifier and found it lost mains power whenever stairs lights were on. I also observed that four or five lights in the stairs did not illuminate and some push buttons didn't activate the lights. That one had me thinking for a while and I drew this diagram to understand what could possibly be going on there:   Head amplifier wall plug N L | | | | |--light bulb--| | |--light bulb--| | |--light bulb--| | X | | |--light bulb--| | |--light bulb--| | |--light bulb--| | | | | | relay | | | | | +-----+ | | N L Mains supply   That turned out an accurate representation of the problem, I found "X" was a badly burned electrical terminal inside a connection box. With relay open, the bulbs happened to be in series in the neutral going to the head amplifier and because its small current draw it had enough voltage to work. With relay closed, only light bulbs before the break illuminated and the head amplifier got the L pole in the N wire through the non-working bulbs, so no voltage to work.

"Mark Zacharias" <mark_zacharias@sbcglobal.net>: Dec 13 09:07AM -0600 Sometimes a small victory makes you feel just as good as a big one.   Picked up a somewhat non-functional Micronta 22-220A multimeter. A little rough but the FET meter circuit worked - voltage readings weren't too far off and the zero control did it's job so I knew all that stuff was OK.   But the resistance function acted as though there was a 4 ohm or so resistor across the leads all the time, and the battery was draining at about 100 mA in Ohms function even with no leads attached.   Of course the 9.1 ohm Rx1 resistor was bad, but replacing it did NOT change the symptom.   After finding a schematic (not many out there...) I did find a component labelled "SA1" shorted at 4 ohms or so. The item resembled an MOV and I can only assume SA stood for spark or surge arrestor.   Removing it mostly fixed the ohms function, and I decided a couple of back-to-back 25 volt zeners would offer enough protection to satisfy my needs.   Still the ohms zeroing was erratic. Cleaning the function / range switch and ohms pot til I was blue in the face did not resolve the problem. It was kinda usable but it kept bugging me.   I tried putting a current meter in series with the test leads but couldn't really get a usable correlation between pushing, poking wiggling the function switch etc and the action of the meter which might zero fine, then show up to several ohms even seconds later with probes shorted.   It occurred to me that I could put a resistor (say 4.7 ohms on this range) across the probes and put a 'scope across that resistor to better see what the DC voltage there was doing.   Oh, yeah. the voltage as viewed on the 'scope varied wildly and looked "noisy" as the funtion switch was wiggled or tapped.   But I had cleaned that switch umpteen times.   Well, there was another switch - a leaf switch, going to the negative battery terminal hiding under the front face and also actuated by the function knob.   A quick cleaning of those contacts and the meter works like new.   A small victory to be sure, but made me feel as good as a big one.     Mark Z.

captainvideo462009@gmail.com: Dec 12 04:25PM -0800 I have two audio amplifier modules I scrapped out of an 8 track player many years ago. I use these to amplify the headphone outputs of two PRC77 military radios tuned to six meters, so that I can monitor on speaker. These modules fit perfectly so I need to retain them if possible. The modules put out about 4 watts each. One module is shorted and it appears to be a bad amplifier chip. There are two output IC's bearing the above number in each module. I can't find a listing for this anywhere. Can anyone help? Thanks, Lenny

M Philbrook <jamie_ka1lpa@charter.net>: Dec 12 07:53PM -0500 In article <c2293d2a-8564-4a03-bcaa-56187555f41e@googlegroups.com>, captainvideo462009@gmail.com says...   > I have two audio amplifier modules I scrapped out of an 8 track player many years ago. I use these to amplify the headphone outputs of two PRC77 military radios tuned to six meters, so that I can monitor on speaker. These modules fit perfectly so I need to retain them if possible. The modules put out about 4 watts each. One module is shorted and it appears to be a bad amplifier chip. There are two output IC's bearing the above number in each module. I can't find a listing for this anywhere. Can anyone help? Thanks, Lenny   are these DIP ic's ? and if so, what pin count are they and do they have the middle legs bonded together from the package?   I can give you a couple of numbers to look at to comparson.   LM380, LM377   etc.. Spregue made some direct replacements etc..   Jamie

N_Cook <diverse@tcp.co.uk>: Dec 13 09:01AM > I have two audio amplifier modules I scrapped out of an 8 track player many years ago. I use these to amplify the headphone outputs of two PRC77 military radios tuned to six meters, so that I can monitor on speaker. These modules fit perfectly so I need to retain them if possible. The modules put out about 4 watts each. One module is shorted and it appears to be a bad amplifier chip. There are two output IC's bearing the above number in each module. I can't find a listing for this anywhere. Can anyone help? Thanks, Lenny   Take some readings off the pins of the working one, while it still is, and try repinning some modern replacement to the shorted one. On removing that , maybe some other number on the underside of it.

Black Iccy <Daedelus@whereamIinvalid.com>: Dec 13 12:11PM +1100 On Sat, 12 Dec 2015 14:11:13 -0000, "Gareth Magennis"   >> Any quick hints or tips from anyone? (It's not the Prescence feedback >> circuit, or the valves)   I think I looked at the right schematic. I don't do repairs these days but going back in time, it was not uncommon for spurious oscillations from the output stages. Not denying that overall looping may be a problem but *some* strange ultrasonics etc would get tamed by tiny (small value) chokes in the plate connections and/or adding resistors into the grid line (so-called grid stoppers). The circuit shows that there are some there. Maybe replace/upgrade? Have you checked for RF band oscillations (in addition to your audio group)?

Phil Allison <pallison49@gmail.com>: Dec 12 05:51PM -0800 Black Iccy wrote: > grid stoppers). The circuit shows that there are some there. Maybe > replace/upgrade? Have you checked for RF band oscillations (in addition to > your audio group)?   ** The OP's Marshall is unstable, oscillating at a few kHz, when gain settings are high. This strongly suggests that positive feedback is the culprit.   It is surprising how little capacitive coupling from the output valve plate wiring to input grid wiring can cause this to happen - with a voltage gain of over 200,000 between the two, even 1/100th of a pF will do the job. The input sensitivity to full power of Marshall models fitted with a master volume is typically 60 microvolts at 6kHz, with all controls maxed. Just plugging an open circuit jack into the input results in oscillation.     ... Phil

"Michael A. Terrell" <mike.terrell@earthlink.net>: Dec 12 02:31PM -0500 > How unAmerican that you do not smother your fries in ketchup! lol     I can't stand ketchup in or on anything, because of the vinegar in it. Eat it if you want to, but keep that garbage away from me. It makes me violently ill.

"Ian Field" <gangprobing.alien@ntlworld.com>: Dec 12 07:15PM "Jeff Liebermann" <jeffl@cruzio.com> wrote in message news:v8mm6blbr9f8p8e7dqmtpll1a4uksjrbmr@4ax.com... > either. Mostly, I try to solder to button cells, not 18650, which > might be different. The paste flux made for copper pipe doesn't seem > to work for stainless. For example;   Some plumbing is stainless and any good plumber's yard will stock flux for it.   The one I bought from had regular and active flux - I bought the latter and it works just fine on stainless.

Cydrome Leader <presence@MUNGEpanix.com>: Dec 12 06:15PM One of my test power supplies in a rather large switching unit from Power One in the SPM5 series. It's basically a mainframe of sorts with power factor correction, timing and a fan on the backplane and 5 slots for various factory installed output modules. Unit is rated 1500 watts. Date code on the outside is 1990.   unit is pretty much this thing with the small slot having a different card   http://www.ebay.com/itm/Power-One-SPM5D2D2V6-Switching-DC-Power-Supply-Unit-Module-Industrial-24V-32A-/111844628139   Mine has two double wide 24 volts 32 amp modules in parallel and the fifth slot filled with a 12 volt 20 amp module. Very handy thing to have around.   The fan started to go crazy as in slowing down and speeding up, stopping and stuff like that, then I noticed the outputs all lost regulation, 12 volts output dropped to about 9 under load and other weird stuff.   About two dozen screws later, the thing opened up and I got the modules out. Fuses seemed ok, and the DC bus had 320 volts on it (sales sheets say 300 volts, but whatever). There's some sort of SCR based active power factor correction trapped under heatsinks, thermal grease and dust. At this point the 24 volt cooling fan was still erratic then basically made sad noises maybe twice a second as it tried to start but didn't have enough voltage. It could not bootstrap or regulate and was restarting. Amazingly the main board only has some 1980s type 8 pin SMPS regulator, not a crazy module thats impossible to work with. Swapped that, no dice. No burned parts, but lots of discolored under the solder mask traces.   To complicate things the control board where the fan attaches was covered in something greasy and apparently corrosive as seen from the blue colors on some leads. Parts cleaner and a brush got that off, mostly.   Probing around didn't show much other than the 24 volts for the fan was pulsating at under 2 volts. It also looked like each module slot has a dedicated winding off the same ferrite transformer to supply isolated power. Those were also way too low. Voltage to one 7805 regulator was zero. It appears that each module gets 320 volts, something around 24 volts and a timing signal and from that they all do their own thing.   Finally found a shorted diode, but the markings were worn off from the cleaning process and whatever. The other similar parts were MUR something and from motorola. I just went ahead and stole one from a backplane slot what would never have a module card edge attached. All the caps on these outputs were rated the same 35V, so it seemed safe enough. I've also noticed the American power supply companies like to keep the part type count low so many parts appear to be grossly overrated, but it keeps assembly simple. Turns out the diode was probably just a MUR115, 150V 1A fast recovery rectifier, judging from the others.   Powered up the chassis and it worked fine. Closer inspection showed one contact for a module slot was broken off from corrosion. Now I have to transplant a heavily glued down card edge connector from the slot I disabled to the slots that does get a card.   Lazy, but it should be OK in the end. Replacement power supplies of this type range from about $150 to $2000 on ebay. Not sure who's paying list prices from decades ago for this stuff.

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