Troubleshooting Rowe R81 Power Supply

Hello! I've got a Rowe R81 with a bum power supply. It has decided to
stop producing the -27VDC rail. I've already replaced more than I had
to, partially due to not knowing a lot about electronics, and
partially because I wanted to make sure it was fixed and had to order
parts anyways. All 3 power transistors (Q1001-Q1003), all 3
electrolytic caps (C1004-C1006), and the voltage regulator IC (Z1001)
have been replaced. But still, when I flip the switch all of the
lights come on, and the -27VDC rail's light fades out over the next
few seconds. It blows the 1 amp fuse every time (F1002 - the repair
manual says 1/2 amp, but the board says 1 amp, and that's what used to
be in there).

So, any suggestions on what to look at next? Like I said, I'm an
electronics novice, but I can find my way around a schematic and a
multimeter. I'm not sure how the transistors at Q1002, Q1006 and Q1007
come in to play on that rail, but that's what I'll be poking at next
unless anyone else has a better idea.

Thanks!

On Aug 14, 6:33*pm, wrote:
Hello! I've got a Rowe R81 with a bum power supply. It has decided to
stop producing the -27VDC rail. I've already replaced more than I had
to, partially due to not knowing a lot about electronics, and
partially because I wanted to make sure it was fixed and had to order
parts anyways. All 3 power transistors (Q1001-Q1003), all 3
electrolytic caps (C1004-C1006), and the voltage regulator IC (Z1001)
have been replaced. But still, when I flip the switch all of the
lights come on, and the -27VDC rail's light fades out over the next
few seconds. It blows the 1 amp fuse every time (F1002 - the repair
manual says 1/2 amp, but the board says 1 amp, and that's what used to
be in there).

So, any suggestions on what to look at next? Like I said, I'm an
electronics novice, but I can find my way around a schematic and a
multimeter. I'm not sure how the transistors at Q1002, Q1006 and Q1007
come in to play on that rail, but that's what I'll be poking at next
unless anyone else has a better idea.

Thanks!

I figured it out! It was one of the 1N4002 diodes in the bridge
rectifier. It was testing a little funny in circuit, but when I
loosened one end to test it out of circuit, it broke into 2 pieces.
That'll do it!

I spent $35 total on what ended up being a $0.03 part. Oh well, at
least the 30 year old electrolytics got replaced, and my soldering
skills are much better. Now maybe I'll tackle the electrolytics on the
amp.... nah.