1986 Fisher television

[jbattles]

looks like your b+ is low check filter cap in ps. i would try that first.

[zeno]

The TP for the main B+ is the cathode of a diode, off the SMPS transformer.
( rear edge of HV PCB ). There may be other diodes off it to run lower
level voltages. The main B+ can be 120 - 140 VDC depending on the set.
Also on the right edge of the HV PCB there is a big black cap. I think its
one of the trouble makers. BUT its been a LOT of years ! The
top vert problem may be another 'lytic IN the vert out. Find the main
problem first. There is probable a beefy diode in the PIN thats in the
hoz out area that shorts on many brands. Lift one end to test.

Zeno

[zchrisz1986]

thanks Zeno, i checked all the diodes and the remaining capacitors i didn't change and all check out okay. i've checked all the resistors.

kind of at a loss now. the Vertical/pcc board had two caps i replaced them with no change.

looks like i'm getting 158v dc past the transformer.

[zchrisz1986]

i replaced all the electrolytic capacitors with no change. still have 4 lines sagging down from the top. it appears the h width adjustment has to be maxed out to even fill the screen. also have a pair of very small lines rolling up the screen. thought for sure it would be a capacitor.

[Alex KL-1]

+1 for suspect PSU.

For indirectly checking the PSU, measure the video amp supply. Is derivated from flyback and usually have 175 to 200V. Suspect if less than 175V. All other flyback derived supplies will be low also then.

Is very uncommon but I've seen sometimes the H tune pulse capacitor (the ones with 1600V ratings in parallel with HO transistor) changing value to less, due to defect (near self destrucion), making image to shrink, but normally this makes all flyback derived supplies to rise (including the video output supply), and affects only the H size. Not seems to be the case, but anyway, if you have a capacimeter...

[zchrisz1986]

I found the service manual!!

anyhow it is low B+ 85volts manual says 110-112v. looks like the SMPS is regulating that way. looking through the schematics now.