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Riddle me this Mr Speaker Relay

Mike Sweeney

Mike Sweeney

Well-Known Member
I think I lost a cap or something on the relay board. Here's the story.. got a beat to hell 2285B but I was able to bring it to life after a fashion :) One of the two filter caps was bad so I pulled it and jumped in a new pair of 10,000 uf caps to test. Hit the power and around 100 volts ( on a variac) I could hit the "tick" of the relay kicking in and I got sound.. not good sound but sound. I went ahead and pulled the tone board, cleaned the pots, rebuilt the power switch and test. Got sound.. better sound. Recapped the tone board.. No sound.. Found one of the jumps ( center ground) came off the old cap still in circuit. Put it back. Still no sound.. no speaker relay click. Check voltages on filter caps.. new pair is +-50 volts.. old cap is -40 +60.. cut it out and put in a new 2nd pair.. now I have + - 50 volts on both pairs. No relay click.. no sound. I ran out of time tonight to mess more with it.. but I'd like to work out what died before I delve into the recapping. I've got the schematics but I figured I would ask first .. and see if someone has some wisdom :)
 
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So a bit more.. I couldn't let it go :) Q810 has 1.6 v on the emitter and should be 0 volts.. collector has 1.09 volts and should be 2 volts. The base should be 0 volts and has 20 volts... I'm guessing C818? odd thing is it's rated at 16 volts so further back is C817 which has a rating of 63 .. I need to measure it tomorrow. Q816 ( double diode) has 43 volts instead of the 40 it should be. The other side Q817 has 47 volts instead of the -42 volts.

The relay coil has 29 volts on Q813 cathode side and 26 on the anode side. The print is saying 35 volts on the cathode side.
 
Hi, I would have to review the schematic for a more informative post but I would check the bias and DC offset. Also the output transistors. The 2270 has protection circuitry that will not let the relay engage if these are not within the range for that circuit. If you have not done so already I would rebuild the entire power circuit with new capacitors. Most of what I have found to be trouble is related to power related or circuit balance. I recently had a pioneer that would not settle in for sound and it turned out to be the potentiometers for the bias. Once replaced and set it behaved beautifully. I will try to look at the schematic and comment further later today unless a more knowledgeable AK er has some input .
 
No caps replaced yet other than the tone board.. and that was because to clean the pots, I had to take the damn thing apart anyways :D
 
Understood, I tried forever to avoid replacing capacitors but it finally came down to the most likely cause of most problems so now I do it as a starting point. If you plan to do this a lot you can make it much more enjoyable by using a desoldering tool like a Hakko 472, this lowered my resistance to replacing them a lot !!
 
I considered getting something like the Hakko I still might :) In other news, I found C817 which was one of my suspects from last night when I pulled it, tested at .14Kohms resistance and 30% loss.. and 1.9 uf which should have been 4.7uf and something like 2 ohms if that. Since there is around 35-40 volts on it, thats bad ;)

I also pulled the relay which tests at 700 ohms on the coil but the whole arm assemble is off center a few degrees. It seems to work but I'll replace it too. The contacts didn't look bad, just a bit smudged. I'm hopeful that cap was my problem child for the relay. I wont know till I get a new relay to put into it. I don't want to put the old one back in.
 
And one more lovely example of 40 year old caps.. C813 rated at 100uf and 16Volts.. reality was 488pF ( yes, pF) and no resistance.. don't think it was doing much.. what I thought was glue was dried out electrolytic .. just a few more to go on the PS.. but I had to order the relay from Digikey so it will be a week before I can power it up and see where i'm at.
bad cap.jpeg
 
petehall347 said:
Recapped the tone board.. No sound ..
no mention of clicks .. ?
Click to expand...
Thats right .. the speaker relay never engages. It was shaky before I started. So far on the power supply board with the relay are two very dead caps.. one is part of the relay circuit. The notes are above. There is zero on the speaker outputs on the scope.. again, no relay. I think the power supply power was pushed over the edge when one of the two double filtering caps failed. I jumped in a new replacement pair which got it up but the 2nd cap instead of + - 50 volts, had -40 and +60.. Now both pairs are temporary jumped in and I have the perfect + - 50 volts.. but the relay circuit had bad voltages.. see above.. thats when I started pulling caps and checking them as a I went.

I'll finish up the power supply recap then add a new relay. If I get sound .. awesome.. if not, I'll go back to the tone board now I have good power. I've kill sound before on a 2226B with bad 1uf caps on the volume control. But until I can get the relay to "click" into place.. it won't matter much :)
 
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