tmsears
Active Member
Yeah I though of that, I have an LED bulb in a utility lamp, Unplugged it, turned the rooms lights off, no dice.
Did you check if the relay clicks with the signal cable disconnected from the power amp board?
Might help fast-track isolating the problem to a single board if that's an option.
I'd check the copper-foil polystyrene caps and make sure they're not touching anything else, probably a silly suggestion but they are a bit sensitive/microphonic.
There's two on the main board, and four on the flat amp board (phono probably irrelevant).
Might help fast-track isolating the problem to a single board if that's an option.
I'd check the copper-foil polystyrene caps and make sure they're not touching anything else, probably a silly suggestion but they are a bit sensitive/microphonic.
There's two on the main board, and four on the flat amp board (phono probably irrelevant).
tmsears
Active Member
I just got around to trying this, and I really wish I hadn't.
I don't know what happened. First I hooked up the dim bulb tester and tried powering up the amp without the signal cable connected to the power amp board.
The bulb stayed dim and no relay click was to be had. So I unplugged the tuner input cable from the selector board and plugged it into the main amp signal plug instead..
Powered the unit back on and the light bulb started going bright then dim, them bright....not good I thought.
So, I put everything back to the way it is supposed to be and powered it back up, bulb still does the same thing, no relay click.
Bulb just goes bright then dim, back and forth..... I am too scared to plug it straight into the wall now...
Oh dear!
That seems really strange though since it's just the small signal input... are you sure it's not something else?
You got the Auto A switch off? It only does that bright/dim cycling thing when in A on DBT normally (not enough power). Should be in AB on DBT.
Edit - have you / had you tried it on the DBT since you finished rebuilding/adjusting it? I wonder if the idle is higher and stopping it from engaging, or the new relay has slightly different values. Seems unlikely if you've got the 150W in there though. I'd try lowering the idle trimmers and see if the click comes back, definitely don't take it off the tester until it clicks.
That seems really strange though since it's just the small signal input... are you sure it's not something else?
You got the Auto A switch off? It only does that bright/dim cycling thing when in A on DBT normally (not enough power). Should be in AB on DBT.
Edit - have you / had you tried it on the DBT since you finished rebuilding/adjusting it? I wonder if the idle is higher and stopping it from engaging, or the new relay has slightly different values. Seems unlikely if you've got the 150W in there though. I'd try lowering the idle trimmers and see if the click comes back, definitely don't take it off the tester until it clicks.
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tmsears
Active Member
Update: I unplugged the amp and looked around for and obvious reason why the amp would be short circuiting when I noticed that one of the solder joints for the ground rail on the main board was not formed all the way around - light was showing through the joint. I decided to go ahead to fill it all the way in while waiting for a miracle (I am poor). I unplugged the main input cable and check for anything amiss - I had folded some poly caps over on the phono/equalizer board when I put my fat hand in there to unplug and plug the input plug back in. Bent those back, and plugged the main signal cable back in and tried again. Bulb stays dim now, and the relay did click on, but it took it longer than normal. That is where I am at this point.
EDIT - it now takes 16 seconds for the relay to click on instead of six. but maybe because still on DBT?
EDIT - it now takes 16 seconds for the relay to click on instead of six. but maybe because still on DBT?
tmsears
Active Member
No I put it the DBT on once and that was when I figured I had to use a larger than 60 watt bulb, you had said it needed to be 77 or larger. Tonight for this I have been using a 100 watt.
Haha yeah that sounds good to me! Phew!
Those small signal input cables can't really hurt anything, but keep it on the DBT (and turn the idle down if you want) while you play around with the hum thing, just to be safe. I've definitely bumped things before and not even realised.
Edit - 100W is minimum for this amp (I actually said I tried it on 77W and it didn't click). It would click faster with the 150W which is why it might seem strange to you now. I didn't time mine but it took aaages to click with the 100W too, so yours sounds perfectly normal!
Edit 2 - Hey, I wonder if your bad ground rail solder joint might have caused the hum? Probably being overly optimistic.
Those small signal input cables can't really hurt anything, but keep it on the DBT (and turn the idle down if you want) while you play around with the hum thing, just to be safe. I've definitely bumped things before and not even realised.
Edit - 100W is minimum for this amp (I actually said I tried it on 77W and it didn't click). It would click faster with the 150W which is why it might seem strange to you now. I didn't time mine but it took aaages to click with the 100W too, so yours sounds perfectly normal!
Edit 2 - Hey, I wonder if your bad ground rail solder joint might have caused the hum? Probably being overly optimistic.
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tmsears
Active Member
Phew is right. I haven't checked the hum yet - the solder ground comment was for documentation purposes to show exactly what I did in case it all went horribly wrong. Think I will be taking a break for the night.
clinic-audio
all on YAMAHA untill 1990
tmsears
Active Member
tmsears
Active Member
Post "phew!" update. Everything seems fine. Tried the 150 watt, and the relay went from 16 to 10 seconds, then back to 6 seconds once off of the DBT.
I Ordered IC102 and IC103 as per Avionic's suggestion. I did something that I would not recommended, and I bought them through eBay......or rather, through ebay storefronts that I think are trustworthy businesses. They are supposed to be new old stock, and are hopefully are not counterfeits. I know that's taking a risk with eBay and all, but I am wanting to wrap this up soon, as I have not had a proper stereo for nearly half a year now. Most of my music is on LP's and I need my tunes!
Update: the IC's are coming from Consolidated Electronics and Universal Semiconductor, so hopefully I won't get burned.
I Ordered IC102 and IC103 as per Avionic's suggestion. I did something that I would not recommended, and I bought them through eBay......or rather, through ebay storefronts that I think are trustworthy businesses. They are supposed to be new old stock, and are hopefully are not counterfeits. I know that's taking a risk with eBay and all, but I am wanting to wrap this up soon, as I have not had a proper stereo for nearly half a year now. Most of my music is on LP's and I need my tunes!
Update: the IC's are coming from Consolidated Electronics and Universal Semiconductor, so hopefully I won't get burned.
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tmsears
Active Member
@zaibatsu , @avionic ,
Well, in my quest for solving my hum issue, I really screwed up.
I went ahead and tried the old "swap the main input signal cable with a input jack cable" after coming up empty handed with the hum problem. I figured if I was gentle and didn't push any components into each other I would be OK to try. I was wrong, I guess.
I plugged the tape 1 input cable into where the preamp cable normally goes into the main board, and powered it up with the DBT in circuit. The DBT, on 150 watt bulb, started to pulse so, I figured I had shorted something...again.
I checked all the components on the phono/eq board to see if I shorted anything there, as that is what happened last time. Everything checked out OK.
Unplugged the tuner cable from the main amp, checked it with nothing plugged into that socket. The DBT bulb once again pulsed, and the relay would not click on. This was expected, and I did it just to be sure, as I had not plugged the preamp out cable back in, I figured, why not check since the DBT is connected.
So I plugged everything back in the way it is supposed to be, with the unit still on the DBT. The relay takes a little while to come on, but on lower voltage, I expected as much. I turn up the volume to check for hum, and of course it is still there.
I unplug the unit from the DBT, and do a visual inspection. Everything looks good. I turn the unit back on. The Relay clicks on. Unit has volume I guess, halfway? Idling.
I start watching a you tube video since the screen is right next to the amp.
A few minutes go by, and I hear the sizzling, crackling noise. I turn my head think, "what the hell?", just in time to see a resistor, R230, Light up like a white Christmas tree light...
I turned the amp off as fast as I could. The coils (of nichrome?) that make up the resistor were pretty to watch cool down.....
So, this is where I say
And......
HELP HELP HELP!!!
Well, in my quest for solving my hum issue, I really screwed up.
I went ahead and tried the old "swap the main input signal cable with a input jack cable" after coming up empty handed with the hum problem. I figured if I was gentle and didn't push any components into each other I would be OK to try. I was wrong, I guess.
I plugged the tape 1 input cable into where the preamp cable normally goes into the main board, and powered it up with the DBT in circuit. The DBT, on 150 watt bulb, started to pulse so, I figured I had shorted something...again.
I checked all the components on the phono/eq board to see if I shorted anything there, as that is what happened last time. Everything checked out OK.
Unplugged the tuner cable from the main amp, checked it with nothing plugged into that socket. The DBT bulb once again pulsed, and the relay would not click on. This was expected, and I did it just to be sure, as I had not plugged the preamp out cable back in, I figured, why not check since the DBT is connected.
So I plugged everything back in the way it is supposed to be, with the unit still on the DBT. The relay takes a little while to come on, but on lower voltage, I expected as much. I turn up the volume to check for hum, and of course it is still there.
I unplug the unit from the DBT, and do a visual inspection. Everything looks good. I turn the unit back on. The Relay clicks on. Unit has volume I guess, halfway? Idling.
I start watching a you tube video since the screen is right next to the amp.
A few minutes go by, and I hear the sizzling, crackling noise. I turn my head think, "what the hell?", just in time to see a resistor, R230, Light up like a white Christmas tree light...
I turned the amp off as fast as I could. The coils (of nichrome?) that make up the resistor were pretty to watch cool down.....
So, this is where I say
And......
HELP HELP HELP!!!
Nooo!
Everything was plugged in perfectly normally and this happened?
Nothing folded/shorting on any boards?
Edit -
Unsolder and check TR142 (green driver transistor A1306 on channel with R230)
I'd also eyeball other flameproof resistors on that channel to see if any are burnt.
Also check TR160 and TR158 the two large (center) output devices.
What do you think happened?
That's really strange, I can't see that you did anything wrong... and usually if you did, things would blow up in milliseconds, not after a few minutes.
Everything was plugged in perfectly normally and this happened?
Nothing folded/shorting on any boards?
Edit -
Unsolder and check TR142 (green driver transistor A1306 on channel with R230)
I'd also eyeball other flameproof resistors on that channel to see if any are burnt.
Also check TR160 and TR158
the two large (center) output devices.What do you think happened?
That's really strange, I can't see that you did anything wrong... and usually if you did, things would blow up in milliseconds, not after a few minutes.
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tmsears
Active Member
Everything was, from what I could tell, perfectly normal. Relay had click on, and the unit was idle. Nothing seemed amiss.
tmsears
Active Member
I looked at the neighboring resistors, they do not appear be physically burnt.
