| "pfjw@aol.com" <peterwieck33@gmail.com>: Mar 20 12:01PM -0700 I have had this beast for about 10 years now, and it has developed a specific symptom - the right channel will cut out entirely - silent-same-as-no-signal on occasion. No pop, no prior acting out, no distortion. Otherwise, no issues. On the output board is a DPST >NC< 24V reed relay. Meaning (to me) that when it goes into protection-mode, the relay gets energized and output is cut. The schematic (HI-FI Engine) seems to bear this out. Picture of board here - down the page. http://members.quicknet.nl/gerard.slikker/hkcitation17.htm There seem to be a number of versions of this relay. Additional part-numbers are: 200-002-7610 and 328-46-B Questions: Anyone else with this symptom in this device? I would hate to replace the relay only to find that something else is going on and the system is doing its job. And, may I substitute any decent 24V DPST relay? I have lots of room to play around. Other notes: a) It is paired with a Citation 19 power-amp, acquired separately. b) I have recapped the power-supply, and the output voltages are as they should be. c) The unit dates c. 1978 Thanks in advance! Peter Wieck Melrose Park, PA |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Mar 20 12:37PM -0700 Update: Computer Components is still in business and has ten (10) pieces in stock made in 1978. They are testing them with the intent of sending me two - at a price, of course. But, I am still wanting to figure out if this is the most likely issue - or should I be looking beyond. Peter Wieck Melrose Park, PA |
| dplatt@coop.radagast.org (Dave Platt): Mar 20 12:38PM -0700 In article <68e28f5e-a05a-44f4-855a-e1d3d460f988@googlegroups.com>, >On the output board is a DPST >NC< 24V reed relay. Meaning (to me) >that when it goes into protection-mode, the relay gets energized and >output is cut. The schematic (HI-FI Engine) seems to bear this out. No, it looks to me as if the circuit works the other way around. The relay is designed to short the output signal to ground *until* the relay is energized. During normal listening, the relay is energized, the contacts are open, and the relay "vanishes" from the audio path. Take a look at how the relay is driven/controlled, from an auxiliary output on the power supply board. >Picture of board here - down the page. http://members.quicknet.nl/gerard.slikker/hkcitation17.htm >There seem to be a number of versions of this relay. Additional part-numbers are: 200-002-7610 and 328-46-B >Questions: Anyone else with this symptom in this device? I would hate to replace the relay only to find that something else is going on and the system is doing its job. Don't have one myself. Here are my thoughts, for what little they may be worth. Since the relay is a DPST single-coil, and only one of the two channels is affected, it seems unlikely that the relay drive is bad... if it were, both contacts would drop to NC simultaneously and both output signals would be shorted to ground. So, if it's a fault in the relay, it must be in the contacts for that one channel - somehow they're sticking closed. I'd be more likely to suspect a reed-relay fault where the contacts _don't_ close properly (due to e.g. lack of contact self-wiping, or the use of a standard reed relay which requires a wetting current when you'd really want a dry relay) and that doesn't seem to be the case here. It _could_ be a case where you've got inadequate current drive to the relay, and for some reason this affects only one of the two reeds, but that seems less likely. I think the first thing I'd suggest, for practical trouble-shooting, would be to catch the problem when it exists, and then trace the signal through the output board... see if you've got audio at J1/3 and then follow it through the output driver and see where it disappears. >And, may I substitute any decent 24V DPST relay? I have lots of room to play around. It doesn't look to me as if the protection circuit is at all sophisticated... the relay is driven from a simple time-delay circuit which is driven by the +24 regulated supply. The relay driver is an MPSA13, which is good for 500 mA continuous. The relay itself is just a short-to-ground NC and the contacts aren't in the normal audio signal path at all. So, it doesn't look very critical to me... any small DPST-NC or DPDT 24-volt DC relay would probably serve (just remember to keep the diode across the coil!) >b) I have recapped the power-supply, and the output voltages are as >they should be. Other possible faults would be a bad 'lytic in the signal path (I've occasionally seen them go entirely open), or bad switch contacts (input selector, tape-monitor, etc.), or a broken solder joint that's undergoing thermal cycling. The "tap the boards with a chopstick" technique might help pin down the location of the fault. I think a signal-tracing exercise would be a good idea, before you replace anything. |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Mar 20 12:55PM -0700 Dave: You are right on the relay operation - I should have caught that - and it makes sense that a power-drop would also drop output. I will signal-trace, but given the symptoms, and with proper understanding of the relay operation, I am even more suspicious of the relay. Most of the caps are new (less than 10 years) and the switches, contacts and input jacks are clean. But, testing leads to better understanding - all good. Thanks for your suggestions! Peter Wieck Melrose Park, PA |
| John-Del <ohger1s@gmail.com>: Mar 20 01:05PM -0700 > Thanks for your suggestions! > Peter Wieck > Melrose Park, PA Many years ago I saw just one DPST protection relay go bad, but it would cause a noisy output or intermittent crackles as the volume was raised as one set of contacts were pitted. But otherwise I'd say if one side is good, it's most likely not the relay as Dave pointed out. The best you can hope for is that it quits entirely. Nothing is easier than tracing a mute audio channel when there's a working one right along side of it, and nothing is worse than chasing an intermittent audio channel when it's working.. |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Mar 20 01:20PM -0700 On Tuesday, March 20, 2018 at 4:05:27 PM UTC-4, John-Del wrote: > Many years ago I saw just one DPST protection relay go bad, but it would cause a noisy output or intermittent crackles as the volume was raised as one set of contacts were pitted. > But otherwise I'd say if one side is good, it's most likely not the relay as Dave pointed out. The best you can hope for is that it quits entirely. Nothing is easier than tracing a mute audio channel when there's a working one right along side of it, and nothing is worse than chasing an intermittent audio channel when it's working.. The first test will be that wooden peg on the relay. Agreed that the quiet failure does not lead to the relay first thing. Peter Wieck Melrose Park, PA |
| Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Mar 21 10:40AM -0400 > Thanks in advance! > Peter Wieck > Melrose Park, PA Seems easy to test--work the relay a few times, hit it with a screwdriver, hair dryer, cold spray.... Cheers Phil Hobbs |
| Ralph Mowery <rmowery28146@earthlink.net>: Mar 20 05:51PM -0400 In article <7vc2bd9erbkjpuoqqrm7quqbpa414p41mj@4ax.com>, etpm@whidbey.com says... > was diagnosing. I don't know how well a digital scope would show that > as I have no experience with digital scopes. > Eric I have a 465B and one of the 200 MHz storage scopes. One thing the storage scope will allow me to do is store a trace on the screen for a one shot event. One thing I can not get the storage scope to do is when I put signals into the x and y axis display for a circle or rotating circle to compair very close frequencies. The storage scope is very poor for that while the old analog 465B works very well. Main reason for wanting to do this is calibrating a time base at 10 MHz from a RF service monitor to a GPS standard. I know there are several other ways around this and have used them. It may be because it is an inexpensive storage scope, a Hanteck one for about $ 300. Not sure if a more expensive one would do better or not for this. |
| jurb6006@gmail.com: Mar 20 07:14PM -0700 >"Not sure if a more expensive one would do better or not for this. " I think it is a limitation of the design. Digital scopes simply are not the same. |
| Terry Schwartz <tschw10117@aol.com>: Mar 20 07:46PM -0700 > >"Not sure if a more expensive one would do better or not > for this. " > I think it is a limitation of the design. Digital scopes simply are not the same. That's crap. I can make my digital scope do anything an analog or storage scope can do, and much more, better, faster, and save the waveforms indefinitely. I can make it act exactly like an analog scope if I want, with much higher resolution, bandwidth, and I'm not limited to seeing one width of the screen. In every way including triggering, the digital scope is more sophisticated and capable. I frankly can't imagine a reason to go back and use an analog scope. |
| jurb6006@gmail.com: Mar 21 12:33AM -0700 >'I can make it act exactly like an analog scope if I want," Oh yeah ? let's see the dot moving across the screen at 1 second per division and demonstrate it principle to students with a battery. I want to see it. A continuous dot moving slowly across the screen. I would bet a case of beer that you can't. Even a raster scan scope can't do it as far as I have seen. Do you have a really special one ? If not, it will blip blip blip refreshing the display and will not give you the dot moving slowly across the screen. If I am wrong, please supply me the make and model and I will reconsider and possibly retract. |
| Terry Schwartz <tschw10117@aol.com>: Mar 21 07:12AM -0700 > >'I can make it act exactly like an analog scope if I want," > Oh yeah ? let's see the dot moving across the screen at 1 second per division and demonstrate it principle to students with a battery. I want to see it. A continuous dot moving slowly across the screen. I would bet a case of beer that you can't. Even a raster scan scope can't do it as far as I have seen. > Do you have a really special one ? If not, it will blip blip blip refreshing the display and will not give you the dot moving slowly across the screen. If I am wrong, please supply me the make and model and I will reconsider and possibly retract. One of my daily use digital scopes at work is an old Tek TDS460a, it'll scan across the screen as slow as 20 seconds/division. It's not a crude dot, it's a real digitized scan with infinite persistence. I can easily demonstrate your simple battery voltage test. It also has a 400 MHz bandwidth for doing actual useful things. How is a moving dot superior to a captured scan that one can actually see even after the signal is gone, measure with cursors, perform math functions on, overlay onto other measurements, store as a reference for recall later, label the axis's, print out, convert to a datastream, export to a file, recreate on a PC,..... ????? This is a very old CRT digital scope, the more modern LCD scopes are even more capable. Analog scopes had their day. That day is over. Test drive any modern digital scope and you'll never look back. You could still drive a Model T cross country, but would you? |
| bruce2bowser@gmail.com: Mar 20 08:28PM -0700 On Friday, February 23, 2018 at 3:45:17 PM UTC-5, Terry Schwartz wrote: > > 5 snap closed ferrite cores around the power cable going into the laptop > > but they haven't helped. Thanks. > Get rid of the inverter. They are all horrendous noise sources. As is the car itself or anything else operating near it. |
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