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Let's Get Technical => Power Amp Tech => Topic started by: bigpoppapump on June 21, 2014, 12:42:13 PM

Title: ADA B200S Repair?
Post by: bigpoppapump on June 21, 2014, 12:42:13 PM
Anyone know where to get a ADAB200S power amp repaired? 10 minutes into band rehearsal, the smell of burnt electronics and loud buzzing coming from the cab. :( not happy. My BS200S is in beautiful cosmetic shape. Would like to get it repaired rather than to simply replace the power amp with something else. Plus, this thing sounded great. I want it back!
Title: Re: ADA B200S Repair?
Post by: Sparker on June 21, 2014, 02:21:00 PM
Hi - where are you based? Is it just the one channel that has gone? Does the other working channel hum as well? Just trying to gather as much info as poss. Let us know. :(
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 21, 2014, 06:01:00 PM
I'm based out of North West Indiana. Both channels are bad. The rig was brought over to band rehearsal and plugged into a marshall 1960a cab. I think someone had changed the Ohm setting on the cab and probably the reason why it fried. We have 2 different bands playing in this spot. At home, I run the ADA split cabs. Less equipment that I have to bring to rehearsal the better. So I tend to run the marshall cab. 
Title: Re: ADA B200S Repair?
Post by: Sparker on June 21, 2014, 11:19:54 PM
Usual suspects for transistor power amp fails are the output transistors and/or the power supply.
Title: Re: ADA B200S Repair?
Post by: rnolan on June 22, 2014, 05:53:17 AM
Hey BP, to blow up the B200s from speaker box impedance, on a per channel basis:
2 ohms (not good, probably gonna cook something, probably output power transistors)
4 ohms, best output from B200 ~124w rms per chan)
8 ohms, fine but less rms ~85 ish
16 ohms still fine (go MJMP) but even less rms ~50 ish but better tops/sparkle..
32 ohms, don't know doesn't sound good.
BUT bad/blown speaker(s), well one cooked one side of my first B2000s, can be fixed though, that amp is still doing well with MikeB.
So worth repairing, schematics etc are posted for you/your tech and MJMP ( :bow: ) is very across B200s...
Cheers R
Title: Re: ADA B200S Repair?
Post by: Sparker on June 22, 2014, 10:37:45 AM
So ... up to you. If you are able to dig in and start pulling parts out by yourself to have a go, and using a meter, etc, to do checks, then go for it. We can advise and guide you through the debug process. Otherwise, there should be techs out there in your part of the world to do it for you (for a price). If the transformer is duff though, could be game over, unless MJMP has spares of those as well???
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 22, 2014, 06:53:50 PM
Thanks everyone. I have some knowledge working on circuit boards. I have about 12 pinball machines that I've rebuild power supply boards etc. I've done a Boss DS-1 mod. Mostly everything I had directions or a parts kit. Anyways, I'll pull this from my rack and dig in and see what my limited knowledge can do. Anyone have the schematics they could send me?
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 22, 2014, 07:22:16 PM
My rig looks so sad taken apart.  :facepalm:

Took the b200s out. Opened it from the bottom. Took the side rails off. Wow this thing is built solid. Anyways, it looks like some transistors were cooked. There are four smaller transistors with what appear to be voltage adjusters? There are 2 together and then another 2 together. I can tell the right transistors on both sides is cooked. The right leg burnt up and the transistors is all toasted and black. The left transistor on both sides look okay?  I can read that they are both a TIP32. I'm unable to identify what the burnt up transistors are. Any idea on a part replacement?

If these 2 transistors are the only problem then I'm completely capable of soldering the new ones in.

Also found something interesting upon opening. There was a blue wire from the transformer with a blue crimp on the end. It's not attached to anything. Any idea what that was for?

I'll put up some pics of everything tomorrow.
Title: Re: ADA B200S Repair?
Post by: Sparker on June 23, 2014, 04:58:54 AM
Schematic and assy dwg attached. If both channels have gone you will need to replace all the transistors on the heatsink (the TIPs and the O/P transistors) even if they look ok. You will also need fresh thermal paste and possibly new insulating pads, try not to re-use the old stuff. From the schematic you should be able to goggle the transistor equivalents, etc, or MJMP might have the proper numbers for them. With the new transistors in place, do a PSU voltage check on the + and - power rails, just to make sure nothing damaged there as well.  :thumb-up:

Edit: Also check as many of the components as you can with the meter (eg. power resistors, diodes) or look for any signs of heat damage before powering on.
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 23, 2014, 05:45:11 AM
Are the O/P transistors the larger ones? 2SA1494, 2SC3858, 2SA1494, 2SC3858? Looks like we have TIP32 and TIP31. The TIP31's appear to be the ones with visible damage. I'll see if I can locate parts. Here's some pics of everything.

Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 23, 2014, 05:46:07 AM
More pics
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 23, 2014, 05:47:15 AM
And for kicks, here's the whole rig minus the Quadraverb.
Title: Re: ADA B200S Repair?
Post by: rnolan on June 23, 2014, 06:29:42 AM
I have a spare US B200s transformer if anyone needs it (wants to pay for shipping). Although if you were going to replace the transformer, go with a toroidal they fit perfectly (bit/top of bolt poking out) and why I have a spare coz we put in a 240v.

I found the cause, if you read the warning, with the switch in mono mode you connected both sides of the B200s together and fried it  :facepalm: (very much the same as if you plugged a speaker lead from A out into B out except there were also 4 speakers in the mix/circuit).  Are the speakers still ok ???  Hopefully there was some protection in the Marshall cab switching thingy... otherwise I suspect they are toast (check them with a meter not a guit amp output signal or maybe more frying...)



When mine fried many years ago it took out only one side and the cause was a shorted speaker

Anyway fix is the same, as Sparker advises, you need to replace the output transistors (IIRC they weren't garden variety ?  the dealer/importer here had parts), we also had to replace a few other bits, it's a long time ago so I have sketchy memory of what else.  We also put a bunch of fuses in various places to make sure it didn't happen again.

Also, I may have said this before, there were at least 2 B200s models I know of, the one that blew was my first one and the first model here (Australia), the B200s I have now was a later, slightly improved model, I don't know what the differences are (MJMP ??) or if/how much the parts schematics are different.
Title: Re: ADA B200S Repair?
Post by: Sparker on June 23, 2014, 06:33:55 AM
Ebay power transistors:- 181048950417. Probably get the TIPs of there as well.
Title: Re: ADA B200S Repair?
Post by: rnolan on June 23, 2014, 06:35:37 AM
1960a
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 23, 2014, 06:43:07 AM
RNOLAN - that's the exact cause. I was just at are rehearsal room yesterday. I checked the back of the cab and that's how it was set. Like I said, another guy plays through the same cab and switched it on me. Never even made it a point to check before I hooked the rig up. Learned the hard way I guess.
The cab is fine. When the B200S blew up, I plugged in a Peavy Valveking and used that for rehearsal.
Title: Re: ADA B200S Repair?
Post by: rnolan on June 23, 2014, 07:08:09 AM
Phew, glad the speakers survived, bummer about the B200s though, and a bloody hard way to learn that lesson.  Again this is why I mentioned before about the later model, IIRC it had better protection ??  I don't think the output transistors changed though.  From the picks (and memory) looks like one of the PACCOM 5W 180ohmJ thingys is also toasted (though may just be the transistor erupting on it ??).
Are the any dates on a sticker of when it was made ? just to make sure you've got the right circuit/schematics etc
Title: Re: ADA B200S Repair?
Post by: rnolan on June 23, 2014, 07:12:08 AM
BTW, nice rig  :thumb-up:
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 23, 2014, 07:22:25 AM
Honestly I think its just the transistor erupting on it. The only tag on it is a serial number:

Serial Number: BB011605
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 23, 2014, 07:24:54 AM
HA! Going back over the pics again. I can already see some bad resistors too. I'm at work right now but I'm going to take a better look at it when I get home.
Title: Re: ADA B200S Repair?
Post by: rnolan on June 23, 2014, 07:42:28 AM
Honestly I think its just the transistor erupting on it. The only tag on it is a serial number:

Serial Number: BB011605
Hey MJMP, can you track that ? IIRC you had some serial number info ?? An sched any light on the different B200s models/circuits/schematics ?
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 23, 2014, 06:54:56 PM
Took the board out of the enclosure today.
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 23, 2014, 06:57:02 PM
Unsoldered wires and removed
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 23, 2014, 06:59:08 PM
Boom.
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 23, 2014, 07:00:34 PM
Revision number
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 23, 2014, 07:04:16 PM
Obviously this isn't the first time this has happened. Here's someone jumper wire. It also looks like all transistors have been replaced based on the look of the solder pads on the underside of the board. These have been changed out before.
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 23, 2014, 07:25:03 PM
Looks like more than the transistors need to be replaced. A couple resistors look burnt. How do I start testing with the multi-meter? I would like to make sure I test everything properly and identify all parts before making a replacement order.
Title: Re: ADA B200S Repair?
Post by: rnolan on June 24, 2014, 06:25:04 AM
Glad you up for the fix, they are good power amps and, IMHO worth it, Sparker and MJMP can (I'm sure will) help you with the measuring.  MJMP/Sparker, is there something that can be put in (fuse??) so this can't happen again ??
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 24, 2014, 07:03:36 AM
So, I've been staring at the schematics on and off. Without testing each component, I can't properly prove my theory.

I'll isolate this to just one channel right now.

If transistor Q4 (Tip31) fried, and I visible indicators of R5 R6 and R8 are shown bad, I can only assume that all the components in between have been toasted as well.

The right leg of the transistor has been blown apart. All others were still intact.

I've got a Fluke AutoRanging multimeter and set it to OHMS. When testing a resistor, sometimes I'm spot on, and sometimes it's no where near what the loading chart indicates. Sometimes it simply won't even stop at a number. I've also read that the only way to properly test a resistor is to remove one end from the board. So maybe i've been testing incorrectly the whole time?

It also looks like the little ball capacitors might have blown? There is a little black burn mark at the top of each one. For example:
C3 C4 C5

Not sure how to test those?

Not sure how to determine the best way to test the transistors on the board? Q6 Q7 Q8 Q9?
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 24, 2014, 07:09:19 AM
I'd also be interested in adding a fuse into the circuit. This seems like a lot of work for a stupid stupid stupid mistake.
Title: Re: ADA B200S Repair?
Post by: rnolan on June 24, 2014, 07:26:01 AM
Lets hear what Sparker and MJMP have to add/say, but is it worth the time/effort to repair ??  Your call, I think it is but definitely feel your pain.  So what blows in an B200s when its' outputs are joined ?? In the meantime you need an amp?, I bought a Carvin TS100, coz my B200s is off the road right now, great amp plenty loud, very transparent, weighs a tonne though
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 24, 2014, 07:49:14 AM
Update: I just got schooled on color coded resistors. And yes, the only way to properly test them is to remove one end from the board. I'll attempt to test each one tonight and start marking off bad resistors on the loading chart.

As far as the capacitors and transistors go, not sure how to test/read these yet.
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 24, 2014, 07:53:39 AM
Yes. Hoping I'll hear from them.

And yes. Totally worth repairing. Mainly because I haven't seen too many of these floating around for sale. The enclosure is in fantastic cosmetic shape. Plus I want to keep all ADA gear together.

I can get away without the rig for a bit as I have some other amps to play/practice through. Orange Pix35, Fender Vibrolux reissue. Bunch of fulltone pedals/electro harmonix, TC delays.

Using the peavey valveking at rehearsals. Not the greatest but It gets by.
Title: Re: ADA B200S Repair?
Post by: rnolan on June 25, 2014, 06:38:36 AM
Totally agree, and glad your up for the fix.  When mine fried it didn't take out too many bits and so glad it's still going strong, MikeB (it's now owner) changed out the jacks recently and discovered they have to not earth with the chassis or you get an earth loop.  However, I lost one channel to a shorted speaker, not sure how much damage connecting A and B outs together causes (MJMP/Sparker? they'll come back when they can... :thumb-up: )
Title: Re: ADA B200S Repair?
Post by: bigpoppapump on June 25, 2014, 09:17:56 AM
I'm just worried that I replace the transistors, resistors, and caps the look burnt up, that I plug it in and it fries again because... I missed changing out one bad diode or just.. something. I just want to be SURE I fix everything before putting back together. I'm really interested in somehow putting in a fuse.

I'll get it going one way or another.

I checked into your Carvin TS100. Found one close to home but its a chrome face model and they want about 350.00 for it. I'd rather fix what I got before dishing the money out for a new Power Amp.
Title: Re: ADA B200S Repair?
Post by: rnolan on June 25, 2014, 10:21:18 PM
I don't think the TS100 comes any other way but chrome face plate ?  And they weigh a tonne being all tube, 350 is a good price if it's new though, I think I paid 600 AUD and that was very discounted.  Great amp though IMHO.

Send MJMP and or Sparker a PM now we know why it fried, they should have an idea of what may have blown plugging the 2 outputs together.

Title: Re: ADA B200S Repair?
Post by: MarshallJMP on June 27, 2014, 01:53:40 PM
Hey
Sorry it took so long to reply but i was away for work.Can you email me some pics (close ups and some decent quality)?So i can have a look.Check the resistors (one end loose).Do you have a multimeter with a diode check on it?If so you can use this to check the transistors.But in your case i  would replace them all.It just takes one bad one to blow up the rest.

Now i use a variac to test,this way you can slowly apply more voltage to the amp,if you see the current rise to hard you can turn it off before you blow it up again.

Title: Re: ADA B200S Repair?
Post by: MarshallJMP on June 29, 2014, 12:52:17 AM
I have about 12 pinball machines that I've rebuild power supply boards etc.

So a bit of topic,what pinballs do you have,i also have 7?

BTW you've got mail!
Title: Re: ADA B200S Repair?
Post by: rnolan on June 29, 2014, 01:38:05 AM
Time for "The Who" tribute LOL
Title: Re: ADA B200S Repair?
Post by: RobbHell on June 29, 2014, 10:13:14 AM
Pinball machine that kick's ass! I still Repair and Upgrade my Laser Disc Players lol anyone remember those?
Title: Re: ADA B200S Repair?
Post by: rnolan on June 30, 2014, 04:25:30 AM
Absolutely, I still have a video player (or 2) and a couple of cassette decks...