HP 6227B Power Supply Slave Channel No Volts/Amps

[Karn]

Hello everyone!

New to EEVBlog and new to electronics. Done some minor electronics repairs prior with help, and learning as fast as I can.

I recently picked up a HP 6227B DC Power Supply with an INOP Slave channel.

Referencing the service manual, I shorted both output terminals, set the unit to INDEPENDENT, and tested both channels for Amperage. Master Channel responds within spec (not o-scoped yet) for both VOLTS/AMPS. Slave channel no response.

I checked the strapping on the rear of the unit but was told it's not related to the issue. (As well as it was strapped correctly).

I am currently looking for F2 and F3 fuses and have spent about an hour finding them on the schematics as well as inspecting the unit and I cannot put an eyeball to them, so either I'm more blind than I supposed or they are on the inside of the PCB's. Can someone confirm?

I am reading through section IV and have found the troubleshoot flowchart in section 5.

I am reading through two threads:

https://www.diyaudio.com/community/threads/hp-6227b-dual-dc-power-supply.267935/
https://www.eevblog.com/forum/repair/hp-6227b-dual-dc-power-supply-ripple-in-master-channel/

Additionally, I acquired this unit with all the side panels but with not screws/hardware to install the panels with. Could anyone identify the thread pitch/diameter fasteners I need for these panels' J-clips?

Thank you all and please excuse my ignorance and any dumb questions as I learn!

Edit: OF COURSE as soon as I posted this I realized I hadn't looked underneath the unit, and I found two fuse locations, one was missing a fuse. Will continue to update.

J.

[barshatriplee]

Fuses are often located on the PCBs, so it's not unusual for them to be hidden from plain sight. Replacing the missing fuse is a good first step in troubleshooting the issue with the slave channel.

[Karn]

Found the problem. Q7(B) shorted to chassis-ground on BCE - all terminals. Apparently a portion of the trace on the AI Mother Board directly after where the Q7(B) harness is soldered got absolutely roasted; you can see where the trace has lifted and separated from the PCB. MASTER works, but SLAVE is now stuck in HV condition ~56v.

Short of taking the *entire* unit apart to access the AI Motherboard and risking breaking anything, I think it's just going to live the remainder of its life as a single channel, unless anyone has a donor 6227B with a good PCB! I could not find a used replacement board online or NOS.

Thanks for your suggestion on the fuse.

J.

[Karn]

In this case F2 and F3 are chassis mounted underneath!

[Flare]

If you still need to know, I believe nearly all the screws (including the ones for the J clips) are:
#6 machine screws, 32 TPI, countersunk phillips head, about 7/32" long.

I have the opposite question, does anyone know where I could source the J clips from or have a similar alternative? The two on the bottom of mine are broken. I think they need to be very short to fit, most have their relief cuts longitudinally whereas these have them cut sideways. They are only 12mm long, whereas the standard size for #6 seems to be about 16mm.