04-01-2019, 02:07 PM
(This post was last modified: 04-01-2019, 02:09 PM by ppppenguin.)
I've found I have 2 of these sets and only want 1. They've been untouched since I bought them which is a good few years ago. So I thought I'd run them both up to see what the CRTs and LOPTs are like. Not too worried about anything else though I'd prefer not to have to deal with any other wound components that are faulty. Not planning restoration at the moment. The plan is to keep 1 set and flog the other at Harpenden or NVCF.
I put the one with the less good cabinet on the bench first. My usual way of running up a TV is cautious. Isolating transfomer so I can connect a scope safely. Aurora on Ch1 direct to aerial socket in case the set is rather deaf.
Look for caps across the mains. Both had been removed by a previous owner in this set.
Disconnect the HT and get the heater chain running, using a variac just in case. It worked immediately
Reform the main smoothers with HT PSU and resistor. The leakage dropped quickly to an acceptable level
Run up the HT gently with a variac. I actually used a 1N4007 here as it was easier to hook up to the variac and safebloc.
When all was OK I reconnected the HT in the set.
So far, without doing anything bar resoldering a detached lead to the line scan coils, the sound has appeared. Fair bit of hum/buzz but I don't care at this stage. Video present on the CRT cathode. Frame timebase running but not locked. Line timebase running but way high frequency, won't go below 25kHz. Plenty of drive to the LOP stage but as you'd expect it's not doing much at that frequency. Tiny sparks where you'd expect rather bigger ones and a few kV of EHT. The EY51 can't be doing very well at the high frequency. Nothing overheating or looking like it's unhappy.
Not a bad start. I need to manipulate the chassis so I can get at the 100pF preset horizontal hold control. Once the line oscillator is running at the right speed I reckon I'll get EHT and first light. Long time since I've played with an ion trap magnet but it looks like it's not been disturbed.
Not having looked at the VT4 circuit for a long time reminds me that it's a relatively complex set for its day, with flywheel sync and sophisticated AGC.
Service data available from http://www.thevalvepage.com/tvmanu/pye/body_pye.htm including a handy note on adjusting ion traps.
I put the one with the less good cabinet on the bench first. My usual way of running up a TV is cautious. Isolating transfomer so I can connect a scope safely. Aurora on Ch1 direct to aerial socket in case the set is rather deaf.
Look for caps across the mains. Both had been removed by a previous owner in this set.
Disconnect the HT and get the heater chain running, using a variac just in case. It worked immediately
Reform the main smoothers with HT PSU and resistor. The leakage dropped quickly to an acceptable level
Run up the HT gently with a variac. I actually used a 1N4007 here as it was easier to hook up to the variac and safebloc.
When all was OK I reconnected the HT in the set.
So far, without doing anything bar resoldering a detached lead to the line scan coils, the sound has appeared. Fair bit of hum/buzz but I don't care at this stage. Video present on the CRT cathode. Frame timebase running but not locked. Line timebase running but way high frequency, won't go below 25kHz. Plenty of drive to the LOP stage but as you'd expect it's not doing much at that frequency. Tiny sparks where you'd expect rather bigger ones and a few kV of EHT. The EY51 can't be doing very well at the high frequency. Nothing overheating or looking like it's unhappy.
Not a bad start. I need to manipulate the chassis so I can get at the 100pF preset horizontal hold control. Once the line oscillator is running at the right speed I reckon I'll get EHT and first light. Long time since I've played with an ion trap magnet but it looks like it's not been disturbed.
Not having looked at the VT4 circuit for a long time reminds me that it's a relatively complex set for its day, with flywheel sync and sophisticated AGC.
Service data available from http://www.thevalvepage.com/tvmanu/pye/body_pye.htm including a handy note on adjusting ion traps.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv