Help: WPC (S) Sound board&#039;s amp blow

5/31/16 update **blew the 2030. Replaced. Cab side works fine. Something is still funky with the backbox side of the board. Amp blows at volumes above 15.

2030 replaced on Popeye but still not working. The journey continues****

I was working on diagnosing why only my cab speaker was working on my JM. Whole other issue...

So i go to swap the sound board from the popeye to the johnny to see if it was the board and not the speakers. It seems it was. So, I go to put the board back in the Popeye and turned it on. Seemed fine but then the audio started to crackle then the amp (transistor? TDA2030AV) started to smoke....... I quickly turned it off.

LIKE A FREAKING IDIOT I look around to see what is messed up. I see its the amp so......I put the Johnny board into popeye......( I know I deserve what I get) I turn it on and I here a pop, QUICKLY I turned the machine off. And as can imagine not only did I have the issue with my backbox speakers but now the Johnny board's amp (I assume) is blown.

So I check voltages on Popeye. I need to do them again but it seems like the sound AC is 20V (should be 18). The pnes on Johnny seem fine. Just trying to figure out what I blew. I think....based off the manual it may be the transformer........agggggg b/c it says the 18v AC comes from there......COULD be wrong, I didn't have a lot of time this morning so I just did some surface checks and tests.

SO I will be testing more to see where I went wrong (and if anyone has a suggestion why the cab speakers worked and the DMD ones didn't in Johnny....but I am not too concerned with that)

I know I will need new TDA2030AV, what else do I need to check...OBVIOUSLY there is something messed up with the power otherwise the other sound boards amp would not have blown.

Open to suggestions and criticism.

Post last edited 7 years ago.

#2 7 years ago

JJS

agodfrey

Inactive member

Oh and how to test TDA2030AV so I know if both or just one is blown. LOOKS like just one (I can see the melt) but...

#3 7 years ago

JJS

agodfrey

Inactive member

I should add that both games play fine with the sound board out. Nothing unusual.

My thinking is to check volatges at the traditional transformer. Open to suggestions on a place to start.

#4 7 years ago

JJS

agodfrey

Inactive member

Not too sure about the voltages. In the audio board here are the readings I am getting.

J4-1 16v
J4-2 16v
KEY
J4-4 20v
J4-5 20v
J4-6 2.5v
J4-7 2.5v

Now.....I think they should all be 18v.

Oddly JM is also giving me weird readings close to those. And while the board might have been messed up, how would that affect the 18v on JM. AND......what am I missing here......still digging but open to suggestions where to dig....there has to be something wrong with the power somewhere ( I am assuming) as thats the only thing able to mess up the second board...right?

Screen_Shot_2016-05-07_at_2.29.02_PM_(resized).png

#5 7 years ago

D G

Pin_Guy

Pinside member

Having a bad cabinet speaker will eat your audio amps for breakfast.

OP
Quoted from agodfrey:
SO I will be testing more to see where I went wrong (and if anyone has a suggestion why the cab speakers worked and the DMD ones didn't in Johnny....but I am not too concerned with that)

The speakers in the speaker panel and the cabinet speakers are driven from a different amplifiers off the audio board, it's not uncommon to loose one and not the other.

My suggestion is to replace the cabinet speaker and the amps in both boards, then put it all back together to see where you are at.

#6 7 years ago

D G

Pin_Guy

Pinside member

OP
Quoted from agodfrey:
Not too sure about the voltages. In the audio board here are the readings I am getting.
J4-1 16v
J4-2 16v
KEY
J4-4 20v
J4-5 20v
J4-6 2.5v
J4-7 2.5v
Now.....I think they should all be 18v.

Transformer voltages have to be measured across the winding and not to ground, to make an accurate transformer measurement you have to put your meter leads between on J4-4 and J4-6.

#7 7 years ago

GPE

G-P-E

GPE

Omaha, NE

13y 76,800 2,778 4

How are you measuring these voltages?

These are unregulated voltages so being off by a couple volts is no problem.
This is a center tap transformer configuration. When plugged into a sound board, two of the pins (center tap) are directly connected to the board's ground. These two pins would be J4-6 and J4-7. If you are using the board's ground as a reference point for your meter (meter's black lead) then pins J4-6 and 7 should ideally read as -zero- volts.
And voltages measured between ground and J4-1&2 should be equal those measured between ground and J4-5&6 -- *approximately* 18VAC.
Based on the slightly asymmetric voltages for a center tap configuration, I would start with checking your center tap connections from the transformer to J4-6 and 7.

You can also measure these voltages without being plugged in ... you would get 18VAc between center tap and two other sets of voltages and get 36volts between the two outer connections. More info... but wife is yelling "we gotta go no"...

#8 7 years ago

JJS

agodfrey

Inactive member

****I'm onto something!!! See below as I think through it!!!***

So I pulled the DMD speakers and they test at 4 ohms each (as they should) I'll check the Cab speaker. I had to desolder them to get a reading, otherwise it was telling me 0 Ohms (maybe they is significant but it seemed to make sense)

And to be clear these were to different sets of speakers and boards.

At first my JM's cab speaker worked but not the DMD ones. It seemed like it was maybe the speakers so I wired the DMD speakers to Popeye. All seemed well (they seemed to work) and then I was pulling them off when I must have hit something (maybe) because the speakers started to pop and U27 starts smoking. SO shut it down. (so this is JM DMD speakers with Popeye)

Then (another big mistake) I put the JM board in Popeye (so JM audio board with Popeye speakers) and it seems like U27 blew again (no smoke but smells funny.

SO.....this got me to thinking. Perhaps Popeye's cab speaker is to blame. I finally found a schematic (doesn't seem to be one in the manuals) to find out what U27 goes to.

So....next step is to test the cab speaker (I need to test that disconnected, yes?)

And I would also like to verify voltages. I can't really have J4 plugged in b/c I am fairly sure it'll smoke U27 more. So I will test unplugged. Ground to J4-4? and then red to J4-1,2,5,and 6.

Cool......that's a direction and a reason! Thanks!

Quoted from Pin_Guy:
The speakers in the speaker panel and the cabinet speakers are driven from a different amplifiers off the audio board, it's not uncommon to loose one and not the other.

Screen_Shot_2016-05-07_at_3.28.51_PM_(resized).png

#9 7 years ago

JJS

agodfrey

Inactive member

BTW, are you Ed K from Great Plains Electric?! You have the best stuff. I have been waiting for the high volatge kits to come back in stock but...sounds like I am going to be getting an amp first

#10 7 years ago

GPE

G-P-E

GPE

Omaha, NE

13y 76,800 2,778 4

To measure AC voltage into board without board connected.
Meter set to AC voltage.
First test lead to J4 plug's pin 7, other lead to pin 1. This is measuring center tap to outer tap and should read about 18VAC.
Next - same test lead to J4 pin 7, other lead to pin 5. This is measuring center tap to the other outer tap and should also read about 18VAC. Based on what you had way above - I don't think you have an issue here other than wondering why you were getting 2.5V on pins 6 and 7 instead of zero volts.

Test the speakers with nothing connected to them. It sounds like one of these might be shorted - that'll definitely take out your audio amplifier.

Yep -- same Ed K from Great Plains Electronics. Taking a week off this coming week and I hope to stock up on kits starting on Monday.

#11 7 years ago

JJS

agodfrey

Inactive member

I had my black on the ground braid. Maybe.... Still concerning... We'll see. I think it's the cab speaker. I have a spare 4ohm , which this good.

If I see that's bad (not sure how it went bad all of a sudden)

After I sort that out I need to figure out why the speakers were acting up in johnny in the first place.... One step at a time.

I'll put an order in this week.

Any other components that are prone to damage from a bad speaker?

#12 7 years ago

D G

Pin_Guy

Pinside member

http://mirror2.ipdb.org/files/1000/Williams_1992_The_Getaway_High_Speed_II_WPC_Schematics_Revised_May_17_1993_.pdf

Quoted from G-P-E:
First test lead to J4 plug's pin 7, other lead to pin 1. This is measuring center tap to outer tap and should read about 18VAC.
Next - same test lead to J4 pin 7, other lead to pin 5. This is measuring center tap to the other outer tap and should also read about 18VAC.

If you look at the first diagram in the WPC Schematic manual, it will give you a clearer understanding of what you are measuring here.

#13 7 years ago

JJS

agodfrey

Inactive member

I pulled all the speakers. Dmd tested about 3.6 ohms (rated at 4) cab speaker had a hair pin between the tab and the body........the magnet sucked it in.......so yeah when I pulled that it tested at 0 ohms....so there we have the culprit.

Popped a new one in. Need to put my order in on Monday for the amps. Then I'll see what's what.

Still need to test volatges to be sure but the fact that the speaker was shorted out and is now 0 when disconnected ....yeah....

Thanks everyone for helping me to figure this out. Not out of the woods but seeing the light.

Every issue is a new thing I learn

#14 7 years ago

JJS

agodfrey

Inactive member

Putting my order together. Added some TDA2030AV and also TL084CN. I am going to pull the board and see if I can see any other components that failed and may have caused my original issue with Johnny. Ohh the journey!!

#15 7 years ago

GPE

G-P-E

GPE

Omaha, NE

13y 76,800 2,778 4

Probably just the audio amp so start with him.

#16 7 years ago

JJS

agodfrey

Inactive member

ORDERED!! Fingers crossed!!!

#17 7 years ago

KFC

kungfucop

Pinside member

Vancouver, BC

11y 37,400 206 15

Same thing happened to me. I removed the backbox speakers to refinish the backbox. Accidentally pinched the speaker tab when remounting the speaker which made the tab touch the speaker housing causing a short. The audio would crackle and eventually the sound amp or voltage regulator chip (I forget which) on the sound board got so hot it smoked and physically blew up.

Bent the speaker tab back out, replaced the blown up amp or regular chip and all is good.

2 weeks later

#18 7 years ago

JJS

agodfrey

Inactive member

OK. finally got around to putting the new amps in. Mostly bad news but some good news.

On the JM board the cab speaker worked great. The backbox speaker was a kinda ok but seemed like it was slightly off. I had the volume at about 5 or so maybe 10. All in all it worked. So I turned the volume up to like....15 or MAYBE 20 and it seems like the amp blew again. And the 2030 & heat sink for the backbox got really hot. I tested the speakers before putting the new amp in and both tested at 4ohms. What do you think is next for me to check?

As for the popeye seems like I blew more than the amps as even with new amps I am getting nothing out of the speakers. Again, all speakers tested good at 4 ohms or whatever they were supposed to be ( I think one of them is slighlt higher maybe)

A little bummed as it takes me forever to get time to sit down and do board work. And bummed that I (possibly) blew another amp......sheesh.

I added some TL084CN to my order but did not install them. Do you think it's worth trying that route? I think on the JM board there might be more to it since the backbox speakers failed before so maybe there is a....resistor that went bad??? Tested a bunch of them and they all seem in spec....But when I put the volume above 15 it 'seems' to blow and won't wok again at lower volumes.

#19 7 years ago

JJS

agodfrey

Inactive member

Looks like I might need to replace r43. Not sure if that is my issue but while it tested ok (15 ohms) it's looking a little crisp. It's 15 ohm 1/4 watt. Radio Shack carried 15 ohm 1/2 watt. Are these a suitable replacement or does it need to be 1/4?

#20 7 years ago

JJS

agodfrey

Inactive member

I was reading that the 10,000uf 35v can fail. How do I test those? Maybe thats what i blew on my Popeye. Tough road of testing...

#21 7 years ago

MVM

markmon

Inactive member

Hillsboro, OR

13y 98,300 13,010 21 81

On that Johnny, if both speakers are testing at 4ohm, make sure they are wired in series not in parallel. The amps are not 2 ohm stable.

#22 7 years ago

BOB

bobukcat

Pinside member

9y 99,550 5,463

OP
Quoted from agodfrey:
Looks like I might need to replace r43. Not sure if that is my issue but while it tested ok (15 ohms) it's looking a little crisp. It's 15 ohm 1/4 watt. Radio Shack carried 15 ohm 1/2 watt. Are these a suitable replacement or does it need to be 1/4?

It is always safe to replace with a higher power rated resistor but the higher rated one will be physically larger, usually 1/4 -> 1/2 Watt is not a big enough to cause a space problem.

#23 7 years ago

JJS

agodfrey

Inactive member

Thanks. I kept the same wiring as before. But worth triple checking! Never know!!

#24 7 years ago

ARS

thedefog

Pinside member

OP
Quoted from agodfrey:
I added some TL084CN to my order but did not install them. Do you think it's worth trying that route? I think on the JM board there might be more to it since the backbox speakers failed before so maybe there is a....resistor that went bad??? Tested a bunch of them and they all seem in spec....But when I put the volume above 15 it 'seems' to blow and won't wok again at lower volumes.

What are your voltages going into the audio board?

A shorted cap could cause an amp to burn up, especially after you've ramped up the volume and the power draw increases. I've seen this a few times with Class D audio amp tinkering.

If your time is limited and you don't have time to investigate, it might be best to send it out. A bad OpAmp probably wouldn't burn up the amp, you'd just have no output.

#25 7 years ago

JND

_litz

Inactive member

Alpharetta, GA

11y 33,900 510 7

99.9% of the time, if you don't have a shorted speaker, you've removed the power board and pinched a speaker wire when reinstalling the power board. It's very very easy, since the speaker wires are very tight around the upper left corner of the power board.

#26 7 years ago

JJS

agodfrey

Inactive member

Quoted from thedefog:
What are your voltages going into the audio board?
A shorted cap could cause an amp to burn up, especially after you've ramped up the volume and the power draw increases. I've seen this a few times with Class D audio amp tinkering.
If your time is limited and you don't have time to investigate, it might be best to send it out. A bad OpAmp probably wouldn't burn up the amp, you'd just have no output.

I'll measure again. But I think they all checked out. I see a 15ohm resistor that looks pretty crispy. At the very least that's an easy fix to fix that one. I'll look again at the voltages as the sounds like the symptoms I am experiencing. I'll also re-check my wires. But like i said, it works, then I turn up the volume and the amp blows.

Quoted from thedefog:
A bad OpAmp probably wouldn't burn up the amp, you'd just have no output.

As for the Popeye I have no output at all after putting new amps in. So maybe it's the opAmp?

#27 7 years ago

JJS

agodfrey

Inactive member

Quoted from _litz:
99.9% of the time, if you don't have a shorted speaker, you've removed the power board and pinched a speaker wire when reinstalling the power board. It's very very easy, since the speaker wires are very tight around the upper left corner of the power board.

This could explain why it failed in the first place...maybe. I 'should' have some time to do bench testing this weekend. I have some new audio caps and new amps coming in. If all else super fails I will send it out. But I would rather learn and spend $40 on parts than learn nothing and spend $80. That said....if I destroy the board....welll maybe I deserved it... ha

#28 7 years ago

ARS

thedefog

Pinside member

OP
Quoted from agodfrey:
I'll measure again. But I think they all checked out. I see a 15ohm resistor that looks pretty crispy. At the very least that's an easy fix to fix that one. I'll look again at the voltages as the sounds like the symptoms I am experiencing. I'll also re-check my wires. But like i said, it works, then I turn up the volume and the amp blows.

As for the Popeye I have no output at all after putting new amps in. So maybe it's the opAmp?

Just to make sure I understand your timeline 100%:

1) Your JM board was the initial issue. It blew the backbox speaker TDA amp when volume went past 15.
2) You plug in your working Popeye sound board to test your JM's speakers and it worked? This is the part I'm confused about, did you turn the volume up past 15 here?
3) Plugged this same seemingly working board back into Popeye and smoked

4) Replaced TDA2030s on both boards?
5) Plugged JMs back in, got sound at a low volume, then blew it out again past 15.
6) Plugged in Popeye's board, got nothing

Is that correct?

It sounds like boards might not be the issue, but the symptom of another issue, like a pinched power wire like mentioned before or some other thing offboard. The JM is likely the only issue and is causing the problems on both boards, if the working reference board was fine before plugging it in to JM. I'd inspect everything before plugging a repaired board back into JM.

#29 7 years ago

ARS

thedefog

Pinside member

That being said, it is probably safe to try and repair a board, then plug it into Popeye as your test bed to rule out those other issues on the JM. Hard to say for sure, but since JM was the initial issue game, it is likely it is what screwed up your Popeye board, granted everything was plugged in properly. Hopefully, Popeye didn't suffer from cooking that board.

If it works in Popeye after repair, then you know for sure the issue is something else on JM. That is a risk though. But sending it out to be repaired, then popping it back into JM might yield the same result.

#30 7 years ago

JND

_litz

Inactive member

Alpharetta, GA

11y 33,900 510 7

I've seen very few cases where you couldn't just replace the TDA2030A and be back in business.

#31 7 years ago

ARS

thedefog

Pinside member

Quoted from _litz:
I've seen very few cases where you couldn't just replace the TDA2030A and be back in business.

Yep, they're usually the failure point due to heat. That, and the caps for the same reason.

1 week later

#32 7 years ago

JJS

agodfrey

Inactive member

ØK. Been super busy but finally got a little time to look at the issue. Here is the timeline because I know it's a bit unclear.

Stage 1
-JM backbox speakers weren't working (before the volume issue. Just stopped working one day- speaker became unsoldered)
-Re-soldered broken wire and still not working (POSSIBLE ground out issue which caused the problem in the first place but speculation)
-Took JM panel to Popeye, speakers worked
-Somehow in the process a hair pin grounded out the cab speaker of Popeye smoking the board.
-After looking around for a minute and figuring the board was the issue (did not know about the shorted cab speaker on popeye yet) took JM board and put it on Popeye. Smoked that one too.

Stage 2
-Got new amps for Popeye and JM. Put them in. JM cab speaker works fine but backbox blows with volume above 15.
-Popeye gets nothing at all.
-This weekend after confirming the speakers were good and wired per the schematics the backbox speaker amp started smoking when speakers were plugged in.

Again, speakers are wired per the schematics (see attachment) which appears to be parallel wiring. Not series. + and - come out of the board. Go to + and - on the left speaker. Then wire goes from + on left to right speaker + passes through a cap, then - on left got to - on right (grounded)

Quoted from markmon:
On that Johnny, if both speakers are testing at 4ohm, make sure they are wired in series not in parallel. The amps are not 2 ohm stable.

I am going to re-measure the voltage out of the board tonight. Also look for shorts. But just an update. Thanks everyone so far.

Screen_Shot_2016-06-13_at_11.32.32_AM_(resized).png

#33 7 years ago

JJS

agodfrey

Inactive member

My biggest thing is ruling out everything except the boards so I know what to fix. Like I mentioned the cab speaker in popeye was grounded out and was measuring 0 ohms. Tested it un hooked and out of the game, 0 ohms. I could also hear it being pulled in all the way when I would power the game on. That has been replaced. Just odd that it would happen at the moment it did.....

What I think happened is the backbox amp was already out on JM. Then the grounded speaker on Popeye took the cab speaker out. Which explains why when I replaced the cab amp on Jm it worked. But something is still wrong with the backbox area. I think I found a resistor that was bad. Could be that or the caps ( I have a new set).

To save me from getting a new set of amps I might replace the resistor and the caps and then see where we are at.

That still leaves popeye that smoking amps left and right. I'll looks at the caps tonight too on that board,

#34 7 years ago

ARS

thedefog

Pinside member

OP
Quoted from agodfrey:
My biggest thing is ruling out everything except the boards so I know what to fix. Like I mentioned the cab speaker in popeye was grounded out and was measuring 0 ohms. Tested it un hooked and out of the game, 0 ohms. I could also hear it being pulled in all the way when I would power the game on. That has been replaced. Just odd that it would happen at the moment it did.....
What I think happened is the backbox amp was already out on JM. Then the grounded speaker on Popeye took the cab speaker out. Which explains why when I replaced the cab amp on Jm it worked. But something is still wrong with the backbox area. I think I found a resistor that was bad. Could be that or the caps ( I have a new set).
To save me from getting a new set of amps I might replace the resistor and the caps and then see where we are at.
That still leaves popeye that smoking amps left and right. I'll looks at the caps tonight too on that board,

If the speaker shorted out the amp, you'll need to inspect all components in the amp section. Resistors/caps/rectifier diodes, etc. No fuse blew in both cases?

From the AC power input, trace all components and focus in that area, granted your logic section is unharmed and your +5/-5 regulators are in good shape. For the board that has zero output, you may wanna inspect that TL084 OpAmp too. If you have a scope, you can probe the input/outputs on that IC to see if it isn't passing an output, or if sound isn't being generated all together at the input, which may indicate a logic issue as well.
TL084_(resized).png

If you don't have a scope, you should be able to use a DMM and probe those pins and see at least some kinda voltage activity on the ins & outs. Just keep in mind not all of the amps on the TL084 may be in use. I'm assuming it is being used a buffer/amp + crossover mixer, so only 3 of the 4 gain stages might be used on it. I don't have a schematic for it, so I'm just guessing here. They might all be used, depending on the design.

3 weeks later

#35 7 years ago

JJS

agodfrey

Inactive member

Ok. So I checked the Caps. New caps read 70 and the slowly tick down by .1. (not sure what level to read it at so I picked one that game it a whole number) the old caps skip around a lot then settle at 50 (ohms) then tick down sometimes at .1 sometimes stay.

I assume this indicated bad caps.

Also worth investigating is the above suggestions.

Now if I were to replace the board if the speakers test at 3.6ohms (rated at 4) the volatges check and there are no grounded speaker wires is it safer than not to assume the issue is the board and I can replace the board safely ?

Then of course try to repair the old one?

#36 7 years ago

???

bdaily1983

Inactive member

Grand Rapids, MI

11y 29,150 401 12

Bump

2 weeks later

#37 7 years ago

ARS

thedefog

Pinside member

OP
Quoted from agodfrey:
Ok. So I checked the Caps. New caps read 70 and the slowly tick down by .1. (not sure what level to read it at so I picked one that game it a whole number) the old caps skip around a lot then settle at 50 (ohms) then tick down sometimes at .1 sometimes stay.
I assume this indicated bad caps.
Also worth investigating is the above suggestions.
Now if I were to replace the board if the speakers test at 3.6ohms (rated at 4) the volatges check and there are no grounded speaker wires is it safer than not to assume the issue is the board and I can replace the board safely ?
Then of course try to repair the old one?

To test a cap, you need to cut one leg out of the circuit and use an ESR meter. A multi-meter will really only tell you if the cap is internally shorted, you'll get zero ohms if that is true. The price of an ESR meter would be more than just ordering the caps.

But don't focus on the caps anyway ATM. They seem like an easy fix, but they usually don't fix issues like this. It probably won't do harm to replace them now if you want, but I'd focus on the opamps and other areas.

Start with the source, the power input. Make sure that is in good shape. Good rectifier, good caps, good voltage regulators, etc. That is the most important part. The fuse will prevent stuff from burning up though, so it is still very likely a short on the audio mixing section at the output to the power amp(s). Make sure there are no shorts on inputs & outputs of your signal path. You can probe around with your meter in continuity and look for premature paths to ground.

4 months later

#38 7 years ago

JJS

agodfrey

Inactive member

OK so back at it. Replaced the caps and the 2030 amps. I actually sent it to an amp place to be worked on as the guy there does some pin stuff and he owed me a favor.

So plug it in and it makes a really loud buzz. Pulled it quickly. Checked the board and it looks like some of the traces on the TL084 had bridges. HEY it was a favor and it looks like most was okay.

Anyway, so fixed the bridges and now there is no sound coming out at all. So the tl084s (yes there were bridges on both sockets) may be shot.

I'm going to test with my DMM. What points should i test for voltage? One on input (1) one on output (1) should it be inverting or non input?

Quoted from thedefog:
If the speaker shorted out the amp, you'll need to inspect all components in the amp section. Resistors/caps/rectifier diodes, etc. No fuse blew in both cases?
From the AC power input, trace all components and focus in that area, granted your logic section is unharmed and your +5/-5 regulators are in good shape. For the board that has zero output, you may wanna inspect that TL084 OpAmp too. If you have a scope, you can probe the input/outputs on that IC to see if it isn't passing an output, or if sound isn't being generated all together at the input, which may indicate a logic issue as well.

If you don't have a scope, you should be able to use a DMM and probe those pins and see at least some kinda voltage activity on the ins & outs. Just keep in mind not all of the amps on the TL084 may be in use. I'm assuming it is being used a buffer/amp + crossover mixer, so only 3 of the 4 gain stages might be used on it. I don't have a schematic for it, so I'm just guessing here. They might all be used, depending on the design.

#39 7 years ago

D G

Pin_Guy

Pinside member

OP
Quoted from agodfrey:
So plug it in and it makes a really loud buzz. Pulled it quickly. Checked the board and it looks like some of the traces on the TL084 had bridges. HEY it was a favor and it looks like most was okay.

I think he still owes you a favor

#40 7 years ago

ARS

thedefog

Pinside member

OP
Quoted from agodfrey:
OK so back at it. Replaced the caps and the 2030 amps. I actually sent it to an amp place to be worked on as the guy there does some pin stuff and he owed me a favor.
So plug it in and it makes a really loud buzz. Pulled it quickly. Checked the board and it looks like some of the traces on the TL084 had bridges. HEY it was a favor and it looks like most was okay.
Anyway, so fixed the bridges and now there is no sound coming out at all. So the tl084s (yes there were bridges on both sockets) may be shot.
I'm going to test with my DMM. What points should i test for voltage? One on input (1) one on output (1) should it be inverting or non input?

So he installed sockets on the TL084s and made solder bridges on the sockets? And it wasn't intentional, and he does this for a living? If that's true, that makes me feel better as a hobbyist electronics guy.

#41 7 years ago

JJS

agodfrey

Inactive member