Peavey XR400 (200H Power Module)

[Enzo]

OK, before we do anything else, please do not connect a speaker or other load until this is sorted out.

If you do not have a variac, then PLEASE look up "light bulb limiter", then make one adn use it.

Installing new parts, fliiping the switch to see what burns up is NOT the way to do things. And when resistorsw burn up, installing larger one won;t solve the underlying problem. Pullint a large resistor in place of a 1/4 watty one will keep IT from burning, but it will just move the burning part issue to some other part.


The negative of one filter will be grounded, and the positive of the other filter cap will be grounded - that is normal.

Make sure any filter caps are installed with proper polarity.

I don;t care what has or has not been replaced, any time something goes up in smoke, get the meter out and test every transistor and diode again. New parts can easily have been damaged in the process. And remember, open resistors can damage things as easily as shoprted semiconductors.

[JohnHEW]

Peavey XR400 (200H Power Module).

Hi Enzo,
Thanks for the update.
Light bulb limiter now constructed and selection of bulbs obtained 25W/60W/100W.
Have not yet checked the board -since the last failure. Will check as soon as possible and post results.
John H.

[JohnHEW]

Peavey XR400 (200H Power Module) Failure & Success

Hi Enzo,
Managed to get a light bulb limited constructed (see pics) and obtained a selection of bulbs.
Checked the board again but could not detect anything obvious other than the blown power transistor Q11.
As the amp was built in 1979 I decided to replace all the electros,C7,C9,C15,C16, C17,C18. I managed to get more or less identical Nichicon spares.
Q1 and Q2 had been replaced by 2N3904's. Q4 was eventually replaced with an MPS6530 and Q5 with a 2N3638.
Q3 and Q9 replaced by MJE253's and Q6 with an MJE243 (or so I thought).
Additionally all diodes had been previously replaced.
Connected up the power board (no power transistors in place or wires connected to board) through the light bulb limiter. Filament glowed.
Then started connecting the connectors to the board- orange wires conected -same low glow from filament.
Then connected the red wires -initial low glow- -bright -then reduced to low glow - then conected then pre-amp board -low glow with power led illuminated on front panel.
I then fitted the power transistors -connected through the limiter - ultra bright glow from filament!!!!!!! failure. Took apart and checked the power transistors -all ok -checked the resistors and diodes again all ok. Took out Q1,Q2 Q4 and Q5 again all OK. I was still getting a short between negative input terminal and positive input terminal. Then checked the remaining tranistors Q3,Q6 and Q9. Q3 was OK, as I removed Q6 I noticed my mistake -I had fitted the wrong type -I had fitted an MJE253 instead of an MJE243. Q9 was OK -correct MJE253 fitted. In effect I had fitted 3 x MJE253's. I clearly put this down to my dodgy eyesight. (now purchased a better illuminated magnifying lamp). Anyway, fitted Q6 correctly -connected up through the limiter -dim-bright surge and dim again- yippee! Let it run for a while -all ok and then connected directly to the mains supply- all ok -nothing getting hot and no DC at output. Assembled amp- connected with my speakers and gave it a blast with my guitar. Everything OK- no crackles in pots, reverb working ok. I also fitted a new mains lead as the original had splits in the outer sheathing. Thast is as far as I got so far -some of the chromed nuts on the pots and inputs have some light surface rust which needs removing and then the amp will look spot on- there is no damage at all to the casing. I've got some better quality smoothing caps to fit and obviously the pre-amp to look at some time.
Thanks for your advice Enzo -and the advice to build the limiter -I really see how much of an indespansable device it is. It will certainly help in my next amp projects -restoration of some old British solid state amps. It cerainly makes a difference doing these types of restorations when there is an expert on hand to give advice/direction. Thanks again.
John H.

[Enzo]

Great, success is its own reward.

Stock up on those light bulbs. The thing won;t work using CFLs.

[Ronsonic]

Maybe this is a dumb question in this context .... But it is the sensible question when the priority is getting something working.

Have we called Peavey to check price and availability of a replacement PCB?

Back to you guys and: GET A DAMN LIGHT BULB ON THE MAINS.

[Enzo]

Not exactly sure what you are asking. But that never stopped me before...

This amp is 25 years old, so finding a whole entire board at PV is darn unlikely.

As someone who services amps, the only time I would consider a new board is when the old one was broken into pieces. Cracked in half, I'd fix it, but smashed into bits, then we'd find a new board. Well really a new amp.

Emergencies are in the eye of the beholder. If you are the Van Halen tour with a concert tonight, a few hundred dollars for someone to throw what you need on a plane is no big deal. For a basement band with a demo gig this coming friday, it may be important, but if they had to shell out $200 to get a whole board here, I think they would be wiser to buy a used amp similar to what they have locally, and it will cost less. Or rent something.

This repair has spread out over a month because each voltmeter reading takes an entire day to be interpreted. If this board crossed my bench, I'd bet my lunch money I would have nice clear music coming out of it inside of a half hour. I am not bragging, just that for a competent technician this board is a simple circuit.

If the owner has time and no cash and is forced to repair himself, or if he just wants to learn something about servicing his own gear, regardless of the time, then buying a new board just to hurry things along doesn't serve the purpose.

[Steve Conner]

Jeez! Are you sure your photographs are big enough?!

[l4rtt-1]

peavy xr-400

Hi!

I have this same xr-400 mixer amp. It seemed completly dead, power(indicator) led didn't light up. But when i unplug the upper(upper in the 200h schematic) connector of the transformer secondary and plug the the lower which gives power to the preamp/mixer section and put on a new 2A fuse, the power led lights up when powered up and the DC voltages(about +15,5V and -15,5V) for preamp section are correct(as they are in the schematics). But every time i plug the upper transformer secondary connector to the power amp section, the fuse burns out and so the preamp and power led won't get power either.

So the problem is somewhere in the power amp? When i measure the AC voltage in the upper transformer connector(when it's unloaded) the voltage across Red(R in the schematics) and Red(R) wire is about 69Volts. Is this correct or is there something wrong with the transformer? If transformer is ok, which components should I start checking? Do i need to take the components away from the PCB to test them?

Any help would be great, it would be nice to get this old amp working!

Thanks,

l4rtt-1

[52 Bill]

Welcome to the place.

Yes your problem is in the power amp section, and the transformer is probably ok.

If you want help in fixing it, start a new thread and everyone will be more than glad to help you out. This thread is already finished and way too long to start a new discussion in.

[l4rtt-1]

Ok thanks!