Recent content by Peter S

Hi Joe. There'll be some traffic your way when someone revives this baby (if)

More pics

Hi Folks, I'll pulling the plug on this sick patient. The power supply works, the back plane wiring is intact. Missing knobs, meters, control board, and output transistors. Rack ears are cracked but one side has already been repaired with aluminum angle. If you are looking at this ad, you...

I thought I got lucky but these meters swing the wrong way!

Hi Folks, finally had a moment to look at these two wrecks. One has missing VU meters, the other has meters but only one working. Has anyone found a solution or source for replacement meters? BTW, just had a new customer here who took two PL700's to the scrap yard last week because they...

Slowly coming together! I have spent way too much time on this project! So many modifications to this amp. Initially I dipped the transformer 20 times in electrical vanish to stop the buzzing noise. Fans were replaced with quieter models. I abandoned the idea of making it passively...

With a little help from my friends, I was pointed to C8 on page 4. It is a 2.2 ufd film cap. I bypassed it with a 20 ufd film cap (sledge hammer approach). The response rose at 5 hz...this is probably dangerous! I will try 10 ufd. Could I use a good quality electrolytic rather than a...

On page 4 of the schematic, there is a SERVO/HIGH PASS section but I am unclear as to which cap (or resistor?) could be changed to remove or at least reduce the effect of the high pass filter. Thanks again for all your help.

The next dilemma is a built in high pass filter in the Crest. I have noticed a distinct improvement in the extreme low frequency response of a temporary replacement amp, a Peavey GPS3500. I measured the Crest CA-18 and the Peavey GPS3500 just to make sure I was not imagining things. I...

An update on the Crest catastrophe; The caps from China came in and of course they measure 15,000 ufd instead of 18,000. I could live with that but they are 130 mm tall and the ad claimed they were 118 mm. I was warned..... At the moment, the amp seems to run quietly with four 9,500 ufd...

What about removing / moving / changing the value of R 10 and R 12 on the fan driver board (page 2) The connection of Q 3 and Q 4 to the regulators via R 11 and R 16 (voltage divider) seems to reduce the effect of temperature change unless I misunderstand

So back to the fan issue. I have discovered the location of the temp sensors. The blank terminals must be for use with a different model. The LM35D temp sensor spec claims + 10 mV per 1 degree C. The sensor circuit seems to be working (to some degree, bad pun). Holding a soldering...

Getting in over my head---again. I have been using a Peavey GPS 3500 (about 600 WPC / 8 ohms) and it sounds great. Bass sounds deeper. I have discovered that the Crest has a non-switchable sub-sonic filter....This just won't do. I will have to reconnect the Crest with all the pieces out...

Hi Jim, they are 24 Volt fans but the series trick would still work. I have just discovered this morning that this amp does not have any temp sensing (see pics in entry #47 above). Maybe installing a sensor would solve the problem...No info yet on what sensor was called for.

J4 on the schematic is supposed to be connected to some sort of 3-pinned temp sensor presumably on the heat sink.