Post about differential probes...can't find it

[dmeek]

You can make your own probe for low cost: https://hackaday.io/project/169390-a...erential-probe

Methinks this is a nice idea. One will be appearing on my bench soon

That's a nice little project. I just ordered the PCB from OSH Park. 3 boards for $9.85USD, free shipping. I would power it with a battery instead of AC adaptor and no more lugging my isolation transformer onto the bench.

btw: I have the rest of the schematics for the PF500 if they're needed. I got them at the Loudtech site before they disappeared. The last time I looked at a PF500 I gave up on it and it was trashed. I don't regret it!

[bsco]

That's a nice little project. I just ordered the PCB from OSH Park. 3 boards for $9.85USD, free shipping. I would power it with a battery instead of AC adaptor and no more lugging my isolation transformer onto the bench.

btw: I have the rest of the schematics for the PF500 if they're needed. I got them at the Loudtech site before they disappeared. The last time I looked at a PF500 I gave up on it and it was trashed. I don't regret it!

I am going to give this PF500 a shot....so far the only component I found gone was one of the output fets.....which are on order along with some of the support components should I need them....
Cheers

[Jazz P Bass]

Generally speaking, if you find a blown output fet, replace the IR20957S driver ic also.

[g1]

You can make your own probe for low cost: https://hackaday.io/project/169390-a...erential-probe

Methinks this is a nice idea. One will be appearing on my bench soon

I'm not getting what SG1 & 2 are ? I'm liking not needing a dual-trace though.

[Helmholtz]

I'm not getting what SG1 & 2 are ?

Should be spark gaps realized by layout.
https://hackaday.io/project/169390-a...-probe/details

[nickb]

That's a nice little project. I just ordered the PCB from OSH Park. 3 boards for $9.85USD, free shipping. I would power it with a battery instead of AC adaptor and no more lugging my isolation transformer onto the bench.

btw: I have the rest of the schematics for the PF500 if they're needed. I got them at the Loudtech site before they disappeared. The last time I looked at a PF500 I gave up on it and it was trashed. I don't regret it!

Hope it goes well! Please post the rest of the PF500 as I'd like to see it. Ta!

[dmeek]

I uploaded the PF500 schematics to https://music-electronics-forum.com/...9&d=1606088416

[nickb]

Thx dmeek.

Here is the power amp from that. If a FET is fried, replace both FETs the 4148 diode, 10 ohm resistor and driver chip. No probes required. A not unusual issue is a shorted output inductor which will blow the FETS due to excessive current. Often they are simple enough you can rewind by hand.

[bsco]

That's not the schematic for the board that I have....the board I have has 4 smt transistors between the gate drive IC and the main output fets......the correct schematic is back in post #12....

[SoulFetish]

That's a nice little project. I just ordered the PCB from OSH Park. 3 boards for $9.85USD, free shipping. I would power it with a battery instead of AC adaptor and no more lugging my isolation transformer onto the bench.!

Populated??

wanna sell me one?

[nickb]

That's not the schematic for the board that I have....the board I have has 4 smt transistors between the gate drive IC and the main output fets......the correct schematic is back in post #12....

It's basically the same. In your case replace the driver transistors too. In many ways class D amps are easier to fix than AB.

[bsco]

I have all the parts ordered.....just waiting for them to arrive....
Cheers

[dmeek]

Populated??

wanna sell me one?

Bare boards, All parts are smd. It is designed for 100MHz bandwidth. I might downgrade it to ~10 MHz The opamps I would use are less expensive and draw much less current.

[nickb]

That opamp driving the midpoint drives a heavy capacitive load. I see nothing in the datasheet that says it's not going to hoot like a banshee.

[SoulFetish]

Bare boards, All parts are smd. It is designed for 100MHz bandwidth. I might downgrade it to ~10 MHz The opamps I would use are less expensive and draw much less current.

The board may have a bandwidth of 100MHz, but it would be difficult to compensate the whole array I would think. wouldn't changing the proximity of the 2 EZ mini-hook leads to one another alter the capacitance enough to cause HF errors?

I'm not set up to populate a smd board, you guys ever use a PCB manufacturer to fabricate and populate PCBs for you? what kind of minimum quantity and cost would that entail?