Repairing a CS1000. (newbie)

[AyEss]

Hello guys and girls. Totally new to repairing amplifiers.. So pleasre bare with me This is my very first project...

As the title suggests, Im in the process of repairing a CS1000 amp that i bought for dirt cheap locally to me.
Bought as "faulty", with no plug on it.. I wired up a plug, flicked the switch and it instantly blew the rear panel fuse.
So made up a Current limiting bulb in series, and the bulb stayed bright... So a short somewhere in the amp.
I narrowed it down to the top board, Channel B i believe..
Without the top channel B board connected, the amp powers up and plays lovely...
Anyway, skip forward a few weeks, I manage to track down the parts... I have removed, tested and replaced the shorted T0-3 transistors, also replaced both Driver transistors just for good measure..
I also tested the SAC187 TRIAC's on the rear board, they were shorted, So i replaced them too.
I got recommended to replace them with BTA16-700B's... But i accidently ordered BTA16-600B, But got told that they should be fine, Since they are 600v, and the 700B is 700v...
Anyway, Playing the amp for a bit, making sure all is good, I cranked it up a little, just to "stretch its legs", and instantly heard a fairly loud bang from inside the amp... The amp continued to play music just fine though! and still does...

The issue now is.. Ever since that bang, Ive been hearing hissing through the speakers, when i turn the mixer volume right down, and get a fairly big POP through the speakers every time i turn the amp and mixer on now, Which it didnt do before..
So, Am i on the right path, to thinking the BTA16-600B is what popped?!?
or should running the 600B be totally fine?!?

I inspected each channel board etc, and found no visual signs of a exploded component.. No smells, No black marks on the PCB etc, Nothing... Same as the Rear board where the 600B's are located either...

I dont know why, (maybe because i know very little about amplifier repairs), but the OPAMPS, for some reason, Play heavily in my mind...
Could it have been an OPAMP blown?!? Like i said, The audio still plays fine though, and it goes very loud...
The only reason why i ask, is because upon inspection, there are 4 OPAMPS on each channel board, and they seam to have been replaced in the past, its a random miss-match of numbered chips...
Each board has a mix of the standard 704 13080, a NE5532P, a TL072CN, etc...
Are these all compatible OPAMPS?!?
One of the channel boards has 2x 704 13080, and 2x NE5532P.....
Do these boards require 2x certain ones, and another 2x certain ones?!?
Or should all 4 be the same chips?!?
I have ordered a bunch of NE5532P's.... So should i just replace all 4 on each board, with the NE5532P?!?

Im so sorry for the essay, Im just very new to all this stuff. This is my very first repair project, and really dont want my 1st attempt to be a failure, Im learning so much, But dont know everything yet

Thankyou..

[Enzo]

Stop. Don't throw parts at it. You look to have different ICs on th board, but chances are real good the amp used to work with those in it.

5532 and TL072 are both dual op amps. They will function in one another's place. The 5532 is nominally a lower noise part. Note in the schematic the 5532 are in the signal path. The TL072 is used to trigger the DDT and turn on the DDT LED. It doesn't need to be low noise as it is not in the signal path. You can use a low noise part there, but why bother?

704 13080 is not an op amp, it is an OTA. It runs the DDT level control. Schematic calls for 87478. DOn't worry about that difference.


When amps blow up, it often takes the SAC187s with it. In general, I leave them out until service is done. Don't worry that you already replaced them, just I'd do it differently. Next time...

You replaced shorted TO3s, good, but also you must test ALL resistors associated with them, mainly for opens. All the 10 watt ones plus the small ones. and don't forget those 22 ohm ones for the drivers.

If a bang came out of it, then SOMETHING blew open.

Loud pop at power up? Two things come to mind. One is that a power up mute is no longer working. Alternatively a DC offset in the amp makes the pop.

Just on a whim, I'd check those 5532 output pins (1 and 7) for any DC voltage. I want to see close to zero vDC.

[AyEss]

hello bud, thanks for your reply.

Being a newbie in this.. Unfortunately, Your message makes very little sense to me
So with my channel board have places for 4x DIP8 packages... which ones are the OPAMPS?!?
The TL072CN's?!?

And in regards to the Traic's... So they dont have to be installed? The amp will work fine without them installed?
i THINK, it was the BTA16-600B Triacs that i installed, that went bang...
Because i still get 100% audio... The hissing on idle has only started since the bang, and so has the POP on power up... Even if i turn the mixer and everything else on 1st...

I replaced some T0-3 transistors, aswell as their corresponding Drivers, with MJE340 and 350's.. I did remove all of the Wirewound resistors from the board and tested each one out of circuit.. all came up perfectly within tollerance..

As for the pop on startup... The very moment i flick the power switch on, I get a little burst of DC offset, around 7-9mV, then it gradients off, to 0.4mV at idle.

Like i said, Im very sorry if i come across clueless.. I kinda of am Speaking to me in simple terms, and specific parts/locations, is easier Heck, 4x DIP8 chips on a channel board, and i dont even know which are which!!! This is my very first repair project, Im learning everything from the beginning... Had to watch a youtube video to teach me how to test T0-3 transistors with a multimeter!!!

[AyEss]

Inspect both channel boards.. Both seam to have the DIP8 chips all scrambled up.. Neither boards match up..
Do you happen to know, which chips go into each location? That ive circled with 1, 2, 3 and 4?!?

Thankyou

[Enzo]

TL072 and 5532 are both op amps. The 87478 or 13080 are not op amps. Three dual op amp ICs on the board plus the one other, which is an OTA.

SAC187 - think of them like seat belts in your car. You want them there, but while working on the car, the belts do not have to be there. The car will work fine without them.

DO we have a reason to remove the ICs? Are any appearing damaged? I leave things in place unless I have a reason to change them.

The two small boards are not identical. One is a sort of mirror of the other. Your red circle board appears to be the B channel one

Note ICs 1 and 3 have pin 1 up and ICs 2 and 4 have pin 1 down.
#1 is TL072
#2 is 87478/13080
#3 is 5532
#4 is 5532


Now look at the channel A card.Note the end of the card with connectors is on the left now.

Numbering the same way,
#1 is 87478
#2 is TL072
#3 is 5532
#4 is 5532.

SO the cards are different, and not supposed to "match up".

[AyEss]

You're a star

and yeah, I noticed the both channel boards are basically mirror flips of each other..
The reason why i want to remove the IC's, is because one of them had a leg bent out, making no contact, and since i ordered replacements of them all, I thought id make sure im 100% putting them in correctly. Knowing very little about this stuff, I was thrown a bit, by seeing different code IC's in different slots. So pulling them all out, to replace with new, just to be on the good side, and wanted to know the exact way they should go in
Im having a difficult time enough, trying to learn what i am doing, and trying to repair it.. Last thing i want to do, is put the wrong chips in the wrong places and cause myself more of a headache

The DDT related chip rings a bell though, As the DDT light used to light up when i had the amp plugged into Limiting bulb.. But now if i do it, It doesnt.. So maybe i am on the right lines here, with replacing them too..

Your sir, Are a massive help so far

Will put the replacement IC's in, and see how it goes

[AyEss]

Okay, Removed the rear board Triac's.. the idle hum through the speakers has totally gone, and so has the speaker POP when i power it on
Maybe the BTA16-600B's i fitted, weren't happy, Got told to buy 700B's instead, But i think im will just go with what's tried and true, get some replacement SAC187's..

As for opamps etc, I replaced them all and fitted them in the numbering layout you said. All good

But got another issue.. Just got round to finishing up the channel B board, that originally had the shorted T0-3's, connected it back in, powered amp on dimmer bulb... Still a short somewhere...
Altogether, I removed and tested each T0-3 transistor, Ordered replacements for the ones that were shorted and open, Fitted those... Replaced both the driver transistors with MJE340 and MJ350's....
Removed and resistance checked each white package Wirewound resistor, and replace the ones that were looking brown or out of tollerance..
Removed and checked the two Diodes near the backside of the heatsink..
Replaced all the IC's... in the order you recommended..
Checked every capacitor with a ESR meter.. Every one of them came back well within tollerance...
Went around the board and tapped multimeter on pretty much every resistor on the board, as well as any other parts that i know how to test....
But when board is installed, Dimmer bulb just stays super bright, Suggesting a short...

Any suggestions?!? Any other common issues?!
I dont know where the 22ohm Driver resistors are... What do they look like?
(still learning what every component is... The fact that resistors can look 50 different styles.. Confuses me)

[Enzo]

ON a channel you hsve twelve bbig transistors...TO3. Most of them are 8332 abd 8333. Those are outputs. Near the center are two different TO3s a 6506 and a 6507. Those ar the drivers. There is a 22 ohm 1w resistor near each one, near the 10 watt guys.

[AyEss]

yeah mate.
Ive removed, tested and replaced the t0-3's that showed open or shorted.. Replaced the driver transistors too.. Removed and tested all the White cased resistors and replaced ones that were out of tollerance...
I have also tested all capacitors too, All within tollerance...
But ive STILL got a short somewhere...
Everytime i power the amp up on dimming bulb, with Channel B board connected, the light doesnt dim down...
and i really dont know what else im missing.. Ive checked basically every major component i can think of...

[Enzo]

Well don't get trapped into assuming you have a bad part. Do any of the power transistors have low resistance to ground? As in maybe we left out a mica insulator under one of them? That sort of thing

[AyEss]

nah bud, there arent no mica insulators on any of them.. They just have silicone greese thermal paste, Collector basically in contact with the heatsink..

Update though.. I managed to find the problem.... Being a noob, I did test all the T0-3's.. But for some reason, I missed one out... One thats hidden under the 2 pin connector.. Thats shorted, So got another on order... Fingers crossed this amp will soon be running 100%
Which i am looking forward to, Being my 1st project, Be glad to see i managed to fix it

[Enzo]

Ah, my mistake. I forgot your model is a "wind tunnel" style chassis, so the heat sinks are electrically live so not grounded?

I hope you have found teh problem.

[AyEss]

Amp is now fully running...

A huge thankyou for the help, i seriously couldnt have done it without you..

all faulty T03 transistors replaced, driver transistors replaced, re-capped with nichicon caps, resistor packs replaced, opamps too.
sounds beautiful now

https://www.youtube.com/watch?v=Nkf7265 ... hannel=RGD

So happy my first repair project turned out to be a success Already got another faulty amp on order, for more repair fun

Thanks

[dak]

You might want to read this post concerning Enzo. It may deserve some more prominent notice, particularly on this forum.