Another longshot - Scientific Atlanta PowerVu psu schematic ?

[Vipersan]

Ok ..I have a Scientific Atlanta powerVu receiver on my bench ..
No signs of life ...
Power supply was totally non functional ..
I've replaced the smpsu chip along with a few electrolytics that looked suspect ..and now have some signs of life from the power supply ..though the voltages are all low ..
for example ..what I assume to be the 5v line is at 4v ...so I think more caps are suspect and loading the supply lines..
What I need is a schematic of the power supply ..or any reference to psu repair on these units.
In the back of my mind I seem to remember such discussions in the past ..not neccessarily on our forum ..
Can anyone help with this ?
rgds
VS

 

[Llew]

Which model VS? The D9234 was prone to SMPS failure, and yes, we discussed this model somewhere on the forum some years ago, as I happen to have one of these (to my chagrin).

 

[Analoguesat]

Yes I can recall some discussions about Power Vu psu's as well.

ISTR ralphmagno was involved in some of the discussions as he used to install them for the Yankee war machine in Italy.

Probably 3-4 years ago

 

[Vipersan]

Doesn't say model number ...but does have a cat no. D9223...so would guess this is the number refered to Llew..
rgds
VS

 

[Vipersan]

Thanks for the PDF llew ..some similarities ..but not quite the same ..
Mine apparently has a +24v line as well as +12v -12v +5v as in the supplied schematic ..
Maybe it will help ..?
Lap of the gods atm..
cheers
VS

 

[Channel Hopper]

Edit


http://www.slashdocs.com/mpimux/powervu-receiver-power-supply-circuit-diagram-by-colibri-th-may.html

 

[Vipersan]

Thanx CH ..
Looks like this is the same one referenced by Llew.
..having said that ..there -is- more info ..and every little may help.
rgds
VS

 

[Vipersan]

Still not got this running ..
Components replaced so far include
Electrolytic capacitor C3 C6 C15 C16 C18 C19 C21 C22 C24 C25 C26
All read low esr to some degree
IC 1 uc3842 AN .. faulty non functional
R28 1k pot ...intermittent wiper contact on track
C12 100pf disc ceramic cap ..damaged by me trying to remove the baked brown glue from the psu pcb
Z3 5.6volt Zener ..short circuit
Z4 15volt zener also short circuit ..(on order awaiting part)
TH1 10ohm thermister ..arcing at power up ..and probably responsible for the demise of IC1 ..and the resulting shorted diodes..
The electrolytic caps were just low ESR and needed replacement as a matter of course..
This is turning out to be practically a power supply rebuild ..but will hopefully get to the bottom of it ..
Fingers crossed 'eh Gibertini ?
rgds
VS