Hafler PC-10 help.....

[burntfingers]

Ok, I'm new here, so have mercy... I recently acquired an older Hafler DH500 that had been partially dismantled, in the process of attempted re-assembly, I downloaded the maual, schematics, etc from the web. However, the manual info only appears to pertain to the PC-19 boards, it seems thereare some differences between the pc10 and the pc19, connection-wise, and would appreciate anyone being able to provide the wiring info necessary to get this back together. Specifically, the wiring of the output fets to the pcb(6 wires), as the boards were pulled from the heatsink assembly.

[Dick West]

Can you provide a picture of your PCB?

The DH-500 uses PCBs similar to those used in the DH-200 and DH-220 amplifiers. The very early DH-500 amps used the same PCB as the DH-200 -- with some slight changes in resistor values to tolerate the higher operating voltage. The later version of the DH-500 used the same PCB as the DH-220.

Compare what you have to the wiring diagram for the DH-200. Perhaps this will answer your question.

Do your PCBs have one or two adjustment potentiometers mounted on them? The early version had only one adjustment potentiometer. The later version had two.

A picture will tell us which you have.

[burntfingers]

The board(s) have one pot each, they are labeled PC-10A, oldies... can send pic soon if you'd like.

[burntfingers]

Here is a photo of one of the PC-10A boards in the DH-500.

[Dick West]

I can see that your PCB is very similar to that of the DH-200 but with changes in the direction of those found in the later DH-220/DH-500 PCB.

Regardless, if you study the wiring diagrams for the DH-200, DH-220 and DH-500 you will see that the ordering of the connections remains the same for each of them as compared to the others. The fixing points on the left in your picture show the attachments for wires coming into the PCB and they should correspond to the same as those in the other PCBs. Do some of the fixing points also have a fixing point on the back side? The other PCBs I mention just have eyelets for fixing points whereas your picture depicts what appears to be push on connection tabs. Wiring goes to the PCB both to the front and from the back sides. Do the back side connections have eyelets or push on connection tabs?

The top and bottom points are for the ± DC. The others correspond to the ground, output and loop for the speaker protection fuse. The backside points will correspond to the ± DC to the drains of the MOSFETs. Two holes (one on either side) will be for the drive to the Gates. The large center tab will be for the joining together of the outputs of the MOSFETs (source).

This is difficult for me to describe other than that the ordering of the wiring is the same for all the PCBs, both front and back.

The manuals for the DH-220 and DH-500 should show a picture of the back side of their PCBs. You can follow the traces on them and compare with what you have. If you do this thoroughly I believe you can come to understand that the ordering of the hook up wires is the same.

Perhaps someone else has better info or a better description.

The manuals on-line at WWW.HAFLER.COM don't show this early version of the DH-500 but I can see it is very similar to that of the DH-200 and was evolving to be the PC-19 PCB layout as shown in the on-line material. Other than some variations in parts layout on the PC-10 vs: PC-6 or PC-19 PCBs, the basic circuit remained the same. The main circuit changes between the DH-200 and the DH-220/DH-500 was that the later models added a small DC nulling circuit (hence the 2nd potentiometer or variable resistor) and the first of the 2 pre-driver transistors had protection zeners and were connected from side to side. Otherwise, the ouput from the circuits was identical.

By now I have probably confused you more than to begin with. Good luck....

[burntfingers]

Thanks for all the info, I believe that will help alot. There are push-on connections on both sides of the pcb, I've never seen this type of a connection before on any vintage Hafler board, best guess is they were added on in an attempt for easier removal of the circuit cards. So you've given me alot of good info, I thank you very much for that. One other quick question: I've read some conflicting info concerning the pinout of the Hitachi mosfets, that the pinout does not follow the standard, but I believe I can determine that with a meter.