• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Wanted: Sphinx project 14 service/repair manual (will be rewarded)

theotdf

Member
2018-02-25 12:54 pm
Wanted:

I have been looking for a 'Sphinx project 14' or a 'Sphinx project 4' repair manual for a long time? Possibly for a fee, Do me a PBje if you know something, get well rewarded!

I have the following questions.

How and where do I measure the bias and dc offset and what is the standard setting for this?

Test procedures etc? Schematics?
 

Peter69

Member
2008-02-07 10:52 pm
"Service manual" Sphinx Project PJ14

Hi Theo,

This is the service manual I have from 1992... I put the term service manual between brackets as it contains close to no service information. It does contain schematics, component placement and BOM... but it doesnot say anything about your (and mine) requested information on bias settings and other adjustments that need to be made after service.

Link to Google Drive as this forum only allows PDF's smaller than 2Mb.
Sphinx Project14 service manual.pdf - Google Drive

Cheers,
Peter
 

theotdf

Member
2018-02-25 12:54 pm
Thank you Peter for this addition. I have been looking for this a long time. I hope that i can also solve the BOM with this and make it quieter. I recently discovered when i lower the voltage aprox 200v AC, the 50hz humming, popping noise totaly dissapears, i think the bias is too high on regular voltage. But a strange thing is when i turn down the Pots for the E88CC tubes the 50 humming gets louder. Is this normal?? Maybe its totaly fixed with the BOM Solution. :worship: :worship: :worship:
 

theotdf

Member
2018-02-25 12:54 pm
The pot i ment is (p1 and p2) in the scheme. When i turn down these the humming gets louder. Are these for the grid voltages of the tubes cq Bias?

There are also 3 zenerdiodes mounted on a voltage regulator in the mid of the board. I think it must be a solution, for something. Grid voltage?

Maybe a pair of capacitors mounted on the
rectifier (bom solution) can solve it but the are 4 of them. to witch does it apply? and after apply a test with a lamp and variac is a wise thing to do.

I also discovered when i hook up scope of functiongenerator on the left input of the amp, it cousing a big desaster. the amp is totaly freaking out strange extremely loud screaming noises appear and the test bulbs are burning fully meaning a dead short? Could this be that there is a ground loop from the left input of the amp throug the scope?


Thank you Peter for this addition. I have been looking for this a long time. I hope that i can also solve the BOM with this and make it quieter. I recently discovered when i lower the voltage aprox 200v AC, the 50hz humming, popping noise totaly dissapears, i think the bias is too high on regular voltage. But a strange thing is when i turn down the Pots for the E88CC tubes the 50 humming gets louder. Is this normal?? Maybe its totaly fixed with the BOM Solution. :worship: :worship: :worship: