Schematic for Parasound Zamp ver 1

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I'm currently working on one of these. All i can find is the Ver.3 schematic too.

What's wrong with yours? Curious if it's the same issue "constant relay clicking" - due to DC on the output (right channel)?

I have replaced the outputs (not exactly the same transistors but should be close enough) fixed one channel, but the issue persists on the right channel.
 
Mine is worse than that, the first thing I noticed is that there was no fuse installed in it but the fuse holder had signs of melting so I decided to install a bigger fuse than the recommended one and I noticed smoke coming from the outputs even with the switch turned OFF, any ideas what could be causing this behavior?

Wondering if the Bridge rectifier or the voltage regulator are bad...
 
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I would check all diodes, something must be shorted to let the current through.

It's may also have a relay that has shorted the contacts together, because it should be open until the voltage regulator circuit and DC offset are at a point to allow it to close.

Yes - yours is worse than mine. Any pics? Mine is super clean (no visible burns, marks or over-voltage conditions) just has a bad component that I'm having trouble finding.
 
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Here is a pic of the bottom of mine - curious if yours has these 2 wires and small resistor. Mine looks like a DIY add, so I have taken them all out (didn't help or change my issue)

I had one leg of the "shorted" channels big pink resistor that was un-soldered from the board. Not sure if it was heat or poor soldering, no marks on the board and the solder was fractured, not melted.

The bad output was on the left channel as was this resistor. When I changed everything the left channel is OK (not perfect) but the right channel now has full voltage on the outputs.
 

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Thought I would post here first to see if there are any responses.
I recently moved so I pulled this back out of the closet to see if I can get this running for an office system. Original issue - with a DBT the relay would click in and out every 1/2 second. I tried with 25, 40 and 60w bulbs and the only difference is the speed of the clicking and with a 60w bulb the power transistors would start to heat up.

First thing I did was pull all transistors and test with a DMM and a transistor tester (from eBay) and only found one bad small signal transistor and replaced it with a suitable replacement (c639, with a leg-adj., reversed C2240) for now and will get a correct one once it is back running.

I put all the small-signal transistors back in the PCB, but left out the driver/power transistors to do some testing.
Current issue is -
Left channel 220r resistors (R225/R227) in-front of 0.22r emitter resistors are getting quite hot - small amount of smoke with a 60w bulb in the DBT.
I took some voltage readings and show ~30vDC on those resistors.
The other interesting thing is that I get ~28vDC on the Collector and 24vDC on the Emitter of the power transistors, but when the relays clicks out of circuit (takes 5-6 minutes with the drivers/power Transistors removed) I get -5vAC on the Base and Emitter, but still have 24vDC on the Collector. Not sure what that tells me/you if anything.
If AC is getting through, does that mean a Capacitor is bad? They look OK, no bulging or leaking, but I haven't tested them out of circuit.
I don't have, and cannot find a schematic - so I'm a little lost on verifying resistor values and mainly checked for reasonableness and that none were OL, and I have not found any that seem out of spec.
Included a few pictures in hopes that will assist. Thanks.
 

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I was just given one of these today (original Zamp, not V2 or V3). Reportedly, it has a high-pitched noisy output (or something like that, not sure the user is very reliable source of info). Popped the unit open, and everything looks (and smells) just fine. I'll power up (DBT) this weekend and see what I can find out. Perhaps we can compare notes as we each go along to figure out what, if any, "mods" were made after the fact(ory). Good luck to both of us!
 
I finally got this little Amp on the bench and got it fixed, now I understand why this go bad... Man they run HOT

I have had this one running for a bit over an hour and the heat sink has some parts as high as 81 degrees Celsius, about 182 degrees Fahrenheit.

I have seen some post online about users saying that V1 of this amp runs really HOT but I didn't expect it to be this HOT, what's your experience??
 
I've got two of them, a V1 and a V3.

Fantastic little amps and I also got them dirt cheap, £80 for both off ebay a few years ago.
The V1 is my computer amp and is permanently switched on.
It does not get hot at all. My landline phone sits on it blocking a few vents and the case gets barely warm. Never opened it up.
 
Glad to see the schematic. I have been wondering why mine basically is not that goood sounding. Architecture looks pretty good. Woudl prefer a CM oin the input, but not bad. I wonder, is the basic problem just no where near enough power supply cap? Only so much will fit in that box.

One more project to fiddle with.
 
Me too

Just got a V3 version off Ebay. Looks good and clean inside but runs really hot even when there's only a 2 watt load on it. Supposedly it will go into protection if it gets too hot. I haven't let it get that hot yet. The left channel has a high THD, about .07%. The right channel is .01%. Output looks good on both channels up to 45 watts where it begins to clip. Just put it on the bench today.


If I find out anything I will post here.


I have 2 more of these amps(bridged) I use for my computer system. Haven't had a problem with them.


Gary