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bitrex <bitrex@de.lete.earthlink.net>: Sep 17 10:33PM -0400 I'm trying to repair this vintage programmable analog drum machine on my bench. It was water damaged, and it looks like it's been sitting in a basement and hasn't worked in a very long time. I've cleaned up the PCB and underneath the rust residue it looks OK, and I've replaced all the electrolytic capacitors and removed any signs of corrosion. It's showing signs of life now, and occasionally produces sounds that seem vaguely correct, but still isn't working properly.   Here's the schematic:   http://fa.utfs.org/diy/boss_dr55/dr55_schematic.jpg   It's a pretty crude machine by today's standards - there's no microprocessor. Just what seems to be a CMOS static RAM chip that the patterns are manually bitbanged into by the user in "write" mode, and then clocked out of in "play" mode. The logic outputs of the RAM IC then trigger four different analog sound generation circuits on the right...for example the bass drum seems to be based on a transistor phase-shift oscillator, etc.   The first big problem I see with my scope is that the there's no clock coming out of the clock generator when I try to set the machine to "play" - tracing backwards it looks like the output at pin 3 of the flip flop made up of two sections of a 4011 (what's the deal with those symbols?) is oscillating at about 4 Hz, and the nominally active-low inputs of the flip flop are totally unresponsive to button presses or manually pulling them low with a jumper.   On the scope the oscillation looks like a slow "inverse" exponential decay from high to low, followed by the output of the flip flop slamming low for a little bit and then rapidly coming back up and repeating. It looks like the on-off duty cycle is about 90%.   Any idea what could be going on here?

Phil Allison <pallison49@gmail.com>: Sep 17 07:47PM -0700 bitrex wrote: > low for a little bit and then rapidly coming back up and repeating. It > looks like the on-off duty cycle is about 90%.   > Any idea what could be going on here?     ** Have you cleaned and checked for continuity the normally closed contacts on the Foot Switch jack?   All the switches are likely to have some corrosion and/or grime on the contact surfaces so need a few drops of WD40 or similar.     ... Phil

mroberds@att.net: Sep 18 04:27AM > I've cleaned up the PCB and underneath the rust residue it looks OK, > and I've replaced all the electrolytic capacitors and removed any > signs of corrosion.   Did you notice that C42 (in the clock circuit) is non-polarized?   > "play" - tracing backwards it looks like the output at pin 3 of the > flip flop made up of two sections of a 4011 (what's the deal with > those symbols?)   A 4011 is nominally four NAND gates - inputs A and B, output not (A and B). not (A and B) = (not A) or (not B). I don't know why they drew three of them as invert-then-OR and one of them as NAND, but it's logically valid.   > is oscillating at about 4 Hz, and the nominally active-low inputs of > the flip flop are totally unresponsive to button presses or manually > pulling them low with a jumper.   The section labeled F/F seems to handle the "start" and "stop" front- panel buttons as well as the foot switch. I would expect pin 3 of the 4011 to go high and low as those controls are operated, but not to oscillate like that.   Part of the feedback for the flip-flop goes through the foot-pedal jack socket. Are you sure that socket is OK and not crudded up? Also, are the "start" and "stop" switches really open circuit when not pushed?   If you completely pull the 4011 out of the circuit, apply an 0V/5V square wave clock to where pin 11 was, and the inverse of that clock to where pin 10 was, I think it should make a lot more noise than it does now.   Matt Roberds

Mike Tomlinson <mike@jasper.org.uk>: Sep 18 10:36AM +0100 En el artículo <55fb77d5$0$5643$4c5ecfc7@frugalusenet.com>, bitrex >"play" - tracing backwards it looks like the output at pin 3 of the flip >flop made up of two sections of a 4011 (what's the deal with those >symbols?)   They're the standard symbol for logic gates.   https://s-media-cache-ak0.pinimg.com/736x/a1/72/a6/a172a616d71c340624f75 15b8b4e6d3a.jpg   > is oscillating at about 4 Hz, and the nominally active-low >inputs of the flip flop are totally unresponsive to button presses or >manually pulling them low with a jumper.   Pin 3 (the output) is connected via R95 to two switches. How sure are you that these switches are ok? Could they be corroded inside?   Lift one leg of R95, does the output signal shown on your 'scope at 4011 pin 3 improve?   Swap out the 4011?   -- (\_/) (='.'=) Bunny says: Windows 10? Nein danke! (")_(")

bitrex <bitrex@de.lete.earthlink.net>: Sep 18 06:00AM -0400 >> and I've replaced all the electrolytic capacitors and removed any >> signs of corrosion.   > Did you notice that C42 (in the clock circuit) is non-polarized?   Yep, it's been replaced with the appropriate non-polarized cap.   > to where pin 10 was, I think it should make a lot more noise than it > does now.   > Matt Roberds   Thanks for getting back to me, I'll give your suggestions a try.

TTman <pcw1.cad@ntlworld.com>: Sep 18 04:59PM +0100 er. > low for a little bit and then rapidly coming back up and repeating. It > looks like the on-off duty cycle is about 90%.   > Any idea what could be going on here? The output of F/F pin3 should be static, either 0 or 1. Pressing START will set pin 3 to HIGH and enable the oscillator IC3 pin 11 D18/R78/C41 ensures the flip flop powers up in the STOP state. For IC3/3 to oscillate at a few Hz, something around there is faulty/broken.   --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com

"Ron D." <Ron.Dozier@gmail.com>: Sep 17 07:43PM -0700 I agree with Tom. CFCL's are good possibilities. There are ways to dix the problem. Basically a better repeater.   See if you can correlate to times the lights are on or even the AC blower. Look at alternate sources of light.   You might want to try a cardboard tube over the sensor. You'll have to have better aim, =, but it will cut off the majority of ambient light.   For now, make sure the remote isn't causing it too. Put it in a shoebox when your not using it.   Ceiling fans are another possibility.   I had an issue with an X-10 system not working when the AC blower was running on a carrier 58mVB furnace, A $70 filter installed at the furnace worked wonders. There is no RFI filter which is stupid.   To further help other issues, a bidirectional transorb was placed across R and C.

"Bob F" <bobnospam@gmail.com>: Sep 18 08:56AM -0700 Ron D. wrote:   > For now, make sure the remote isn't causing it too. Put it in a > shoebox when your not using it.   > Ceiling fans are another possibility.   Electrical tape over the IR sensor on the TVs would be one way to test for spurious IR signal problems.

"Ian Field" <gangprobing.alien@ntlworld.com>: Sep 17 08:16PM +0100 "DaveC" <not@home.cow> wrote in message news:0001HW.1B9BFB3100248A5811E4F83CF@news.eternal-september.org...   >> Tim   > Dead. Other with identical markings measure as NPN. What else to determine > from measurements?   You can usually distinguish the B/E junction because it will zener somewhere around 5 - 8V ish.   You need to keep the test current pretty low - you can get ultra-efficient LEDs that give a useable indication at only 2mA. Hook one of those up with an A23 12V keyfob battery and a current limiting resistor.

krw <krw@nowhere.com>: Sep 17 08:05PM -0400 On Thu, 17 Sep 2015 20:16:17 +0100, "Ian Field"   >You need to keep the test current pretty low - you can get ultra-efficient >LEDs that give a useable indication at only 2mA. Hook one of those up with >an A23 12V keyfob battery and a current limiting resistor.   InGaN (true) green LEDs are quite bright at only 1mA. They can be seen at much less than that.

Jeroen Belleman <jeroen@nospam.please>: Sep 18 09:08AM +0200 On 2015-09-17 21:16, Ian Field wrote:   > You can usually distinguish the B/E junction because it will zener > somewhere around 5 - 8V ish. > [...]   You do that with low noise transistors and they'll be useless.   Jeroen Belleman

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Sep 18 10:50AM -0400 On 09/17/2015 08:05 PM, krw wrote: >> an A23 12V keyfob battery and a current limiting resistor.   > InGaN (true) green LEDs are quite bright at only 1mA. They can be > seen at much less than that.   An ordinary 4-3/4 digit DVM on the lowest volts range (400 mV usually) makes a poor man's picoammeter. The 10 megohm ones read 1 LSB (0.01 mV) for 1 pA. Some of the older ones, where the lowest range doesn't have the 10M resistor in parallel, can be much more sensitive than that.   You aren't going to hurt a transistor with a nanoamp of reverse base current, and the measurement is pretty simple.   Cheers   Phil Hobbs   -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics   160 North State Road #203 Briarcliff Manor NY 10510   hobbs at electrooptical dot net http://electrooptical.net

mroberds@att.net: Sep 18 04:35AM > r02455212, demultiplexer for 7 octave keyboard Roland RD 300SX.   I Googled that part number and it seems to also have been used on a semi-recent (about 2012) keyboard, RD-700NX. This guy took his apart to look at it, and provided an inventory of the major ICs:   http://www.pianoworld.com/forum/ubbthreads.php/topics/1815839/NEKID_PICHURES_Roland_RD_700NX.html   > Assuming a spares or repair broken piano is not available. Is the IC > likely to be obtainable through the barrage of scammers, timewasters > and googlead revenue crap, to genuinly purchase one from the far east?   Have you taken the revolutionary step of asking Roland?   Matt Roberds

Clifford Heath <no.spam@please.net>: Sep 15 09:08AM +1000 On 17/09/15 18:39, N_Cook wrote: > pile of doodoo > The die is cracked or failed lead-out wire, on the common for one 8 note > bank of keys.   I read the schematic for my Roland HP3000 once, and thought that chip was probably a custom-programmed CPLD/EPLD. Are you sure you couldn't program such a chip as a replacement?

N_Cook <diverse@tcp.co.uk>: Sep 18 02:05PM +0100 On 15/09/2015 00:08, Clifford Heath wrote:   > I read the schematic for my Roland HP3000 once, and thought that chip > was probably a custom-programmed CPLD/EPLD. Are you sure you couldn't > program such a chip as a replacement?   Probably more difficult than getting an IC out of Roland/Boss. The sort of thing I might attempt if it was a repair job for myself , but I doubt the owner would want to pay me to construct a glorified look-up table and then all the debugging, Plus desolder/soldering .

jurb6006@gmail.com: Sep 17 09:33PM -0700 On Thursday, September 17, 2015 at 1:10:40 AM UTC-5, Ron D. wrote: > From what I have been reading HDMI has no "caption Data" which can be turned on/off. It has to be integrated into the HDMI video permanently.   Then it is a deficiency in the DVR. Where else could it be ?   Onl other thing I can say is go in those DVR menus and look or recording options and maybe they have wher you shut of CC to enable some "cool" feature you never use.   Also go to the website, they all have a website. Put in the model number WITHOUT the brand name first. Put in the search string "firmware". (without quotes) Notice if other brands come up, from one of them you might get firmware.   We could all be wrong here, isn't this format supposed to be the hifi of TV ? Maybe it is like me getting rid of all Windows sounds so I can be onlone and listen to music. i really do not know.   It used to be in the vertical interval in NTSC, which is what composite is. If HDTVs cannot reproduce CC in the highest mode they can otherwise handle, they are in violation of a federal mandate. They deaf community will have their head, and you know what ? Alot of people watch TV with it muted and the CC on even though they can hear. I do hen I watch, my Mother is hard of hearing but the TV has a decent set of speakers on it and she had hearing aids, but we have come to the conclusion that not having these hucksters in our ears is actually better than trying to hear dialog in whispers among all kinds of background street sound going through an echo chamber and overloading the whole story. And I have tried switching it to mono. Sometimes it works, but not all.

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