music fidelity elektra E30 power amp

[valvedude]

hi out there i am working on an  music fidelity elektra E30  power amp with a nasty distortion on both output channels 

 

the amp had been some were else were  some one had done a dogs dinner of a repair job tracks lifted wrong value components fitted 

 

i have managed to get a copy of the circuit rev 4 this unit is 

 

on the circuit it states it uses MPSA 43 and MPSA 93 but in the unit it has MPSA 42 and MPSA 92

 

i put all the right value caps back and resistors

 

got me a bit bamboozled may be some else has had this fault

 

the bad part about this is all the faults  started due to some ones shi? repair job   

 

as you can see on the CRO 1000 HZ in and bingo this rubbish out 

Edited December 18, 2014 by valvedude

[chefjeff]

Well in my opinion you should be working on other projects, say building preamps and such!

[valvedude]

not under stand your comment lol i was asking if any one had seen this fault stay work on preamp lol i take it  you are be sarcastic  

[valvedude]

Well in my opinion you should be working on other projects, say building preamps and such!

[Zaphod Beeblebrox]

The significance of MPSA42/92 vs. MPSA43/93 is that of Voltage. The MPSA42/92 are higher Voltage devices and were likely installed by the manufacturer, since the price difference is inconsequential. 

 

The obvious distortion on one channel may be causing the apparent HF oscillation in the other channel. You should isolate the faulty channel and see if that clears up the instability.