Pye 37K7225
 

Hi.
I am attempting to repair for personal satisfaction an old portable
1979-80 TV.
The problem I have is no picture, no sound and a pulsating power noise.
Any suggestions?
Thanks

Pye 37K7225
 

What's a "pulsating power noise"?

Pye 37K7225
 

"Mr. Land" wrote in message
oups.com...
What's a "pulsating power noise"?


Hmm? 79/80 sounds a bit early for a SMPSU - if there's an overload the PSU
trips then tries to restart, this makes a pulsating or sometimes a breathing
noise.

Pye 37K7225
 

Yes does sound as though it is trying to restart.
Any idea's?

Pye 37K7225
 

"DRead" wrote in message
oups.com...
Yes does sound as though it is trying to restart.
Any idea's?


Horizontal scan transistor maybe S/C?

Horizontal scan transformer maybe shorted turns or insulation breakdown?

Horizontal scan flyback tuning capacitor S/C

The tuning caps often crack or split when they fail, and you should have
done a thorough visual inspection by now anyway! Try disconnecting the
collector of the scan transistor - first test it for S/C then try powering
up with it disconnected. Note that the PSU may not take to being run with no
load so try connecting a 40W or 60W bulb from the feed to the collector to
chassis (GND) See if the PSU fires up and lights the bulb and it wasn't a
S/C transistor, this points to either shorted turns in the transformer or a
load on one of the scan derived supplies S/C - such as audio or vertical
sections. If the PSU still won't fire up its likely the scan transformer
primary winding is shorted to GND or the PSU itself is faulty!

Pye 37K7225
 

"DRead" wrote in message
oups.com...
Yes does sound as though it is trying to restart.
Any idea's?


The set probably contains a Philips chassis - do a search on the model
number to try and find the chassis type, I might just have the schematic!