Warwick PRO FET IV schematics

[Andy S.]

Another project from the shop owner!! Old used amps he took in as trade, with the notion of fixing them and selling them. He's had them for several years and would like me to take a look at them.

One is a Warwick PRO FET IV head. Problem: It let's the smoke out of an IC chip on the main output PCB. And it's not one of the main output Xisitors.

Hit the ON switch, smoke starts leaking out. Turn it of, it stops leaking. (Attempt at humor for the unitiated)

I was scanning the 'net and no one seems to have the PRO FET IV. They have some other Warwick stuff here and there, but not this particular one.

Just would like to know what I'm getting into before I start replacing parts and watching them smoke, too.

[R.G.]

It's probably one of those all-in-one power amp driver chips if it's smoking.

National Semi made one ... um could be the LM391, I'd have to do digging. They are high voltage chips, but sensitive to abuse, particularly over voltage.

Is the power amp otherwise discrete, or is it just the IC drivers and output transistors?

What does the IC look like physically?

[Enzo]

When you were scanning the internet for this drawing, did you contact Warwick itself and ask for the drawings?

[Andy S.]

When you were scanning the internet for this drawing, did you contact Warwick itself and ask for the drawings?

Enzo, Yes, I always try to find the stuff myself first.
I sent an e-mail to their tech support site on their web page. I'll admit I was a bit impatient. Rather than waiting for this coming week to see what reply I get( they're only open M-F, typical biz hours according to the site), I thought I'd ask here. If I could get a jump on it and get it done a few days earlier than waiting. Sorry for the impatience.


R.G.,

It's probably one of those all-in-one power amp driver chips if it's smoking.

National Semi made one ... um could be the LM391, I'd have to do digging. They are high voltage chips, but sensitive to abuse, particularly over voltage.

Is the power amp otherwise discrete, or is it just the IC drivers and output transistors?

What does the IC look like physically?

I'm pretty sure it's not a power output chip. Those are attached to the cooling fins and fan assy. This is a 14 pin configuration. It's a HEF4093BP which according to the NET cross ref site, that's some type of dual op amp. No drawings were available. So, yeh, maybe a driver or preamp of sorts.

On closer inspection, I'm thinking something else cooked it, as two of the pins (1 & 2) were burnt very bad, almost off.

[Enzo]

What power rails are at its corners? Where do the traces wander to?

Are you sure it is not a plain old 4093B? CMOS Quad NAND Schmitt?

My NTE book (shudder) crosses it that way too.

[Andy S.]

Well, it's been two e-mails and just over a week and I've had no response from the folks here in the U.S. for Warwick (DBGTech@ danabgoods.com).

So, I'll try to call them later today, to see about a schematic. Then I may e-mail the international address. (they'll probably refer me back to danabgoods.com! )

As for where the leads go..., it appears they all work their way around that half of the board and are focused mostly with several other small transistors.

Again, this is one of those "projects" the shop owner, or someone else messed with first. It looks like there was a resistor in part of a circuit (evidence of solder and holes in the board) but now it's gone. Several of the small transistors have handwritten numbers near them.

In addition, there appear to be two devices, perhaps thermal fuses of some sort, that are pressed up against the cooling fins. They look similar, but not identical. So I don't know if someone messed with those, either. As for the rails, I haven't gotten to plugging it back in to test, and since I just got the PC back, I've not gotten back to the NTE site to see the pin-out for that chip.

Anyhow, I'll keep you posted on any progress. What an Adventure!!! Following after someone else has pulled parts!! Whew!

But then again, you guys are helping me!!! Some dweeb getting back into it....and for that , I appreciate your patience and knowledge!!


Andy S.