1954 Philco high b+ issue.....

[DaveWM]

you use two 9v connected in series, with the middle connected to the chassis ground, Then you connect the + to one side of a 500k pot (or what ever you have handy) and the - to the other side of the pot, then use the wiper as the AGC, that way you can swing from +9v to -9v relative to ground with the pot.

you can check you setup by using a meter, connect DC neg to ground (center connection of two 9v batteries) and pos to wiper. with the wiper centered you should see 0v moving off center will swing + or -

FYI i had a set that had lots of probs with sync, I thought it was alignment, turned out it was an open .15 cap on the AGC. You nver want to go to alignment unless you are sure it needs it and you have the correct equipment to do it, and even then it takes practice to do it right. Rarely is alignment bad enough to cause really bad problems, you can generally improve a pic some but honestly unless someone has gone in and done "screwdriver drift" its prob not going to be a problem.

other considerations on sync, of vert is ok and horz is not or if horz is ok and vert is not, then its prob not the separator but rather the integrator (vert) or something in the horz osc that is messed up. when they are both out you can assume its the sync signal. then you just have to figure is it the signal to the separator or the separator itself.

[Davala]

Thanks so much! What part of the AGC circuit do I add the battery?

[DaveWM]

hard to read but I think it says 1 meg and a .15 that goes to the plug that ties into the local distant swich (you have tried that right? does it have any effect?). connect up at the junction of that that resistor and cap. You should put a meter on there 1st to maker sure the voltage is somewhere close to zero before attaching (you would not want to hook up to something that has B+ on it).

[Davala]

This model doesn't have the local/distance switch. But pretty much anything on the AGC line is about -2.5 volts. I wonder if the AGC is working inversely. On stations with no signal or weak static the 130B+ is near 135. I'm getting the FM band(I'm sure the tuner is out of adjustment) very loudly and on those loud channels the 130B+ shoots up to 168-170. Even on blank channels where its just static I can move the fine tuning knob and when the static gets louder the voltage increases from 138-160. Also on those FM stations I can see the screen vary with the FM signal.

Hmmmm. Tomorrow I'll try the battery on the AGC line.

[DaveWM]

I would not get too worked up about voltage readings. They assume no signal for starters, and you really should use a VTVM (it prob says so on the sams) after all that is what they used.

[old_coot88]

This is a long shot, but is there a chance the video detector diode coulda been chopped out and then re-installed backward?

I was goin' by your recounting of years ago when the set had been "butchered" and various parts cut out and then re-installed. A reversed v detector diode will display some really bizarre symptoms such as you describe.

(Not sure about the FM audio coming thru, though.) Can't tell from the partial schematic, but does that set have intercarrier sound (sound taken off after the vid detector), or the earlier 'split sound' (a dedicated sound IF strip straight from the tuner)?

Ditto what Dave says about not being overly concerned about those voltages.

[Davala]

I did replace the vid detector recently. After the recap of the set I had dead audio and video. Replacing the diode got me to where I'm currently stuck at. I'll check polarity tomorrow and flip it around regardless.

Yes I did get quite worked up over voltages. They just weren't making sense what was happening. And the higher negative voltage on the IF grids has me bugged.

Browsing on ebay for a VTVM.. Wife won't approve I'm sure.. So many to choose from, and not all are come with leads or that are guaranteed.

Before leaving my parents house I went over every single resistor in the AGC circuit. The circuit was wired correct and resistors were in spec. The 6T8 pin 6(AGC diode plate) the resistance measurement didn't add up. Should have been 1.5 meg but was reading low. I disconnected the mica cap(150MMF) from the AGC diode plate to ground and the the value bumped up close enough to 1.5megs. I'll have to find replacement somewhere. Not sure what its purpose is.

Definitely getting flustered working on this set. Not sure if Philco's quality dropped by 54 or what... This was a very basic 21inch set.

[jr_tech]

*Really* off the wall, but what if the IF amp was oscillating? This oscillation might stop and cause voltages to change when the circuit is probed. Perhaps the FM reception could be explained, as well by the IF acting as a crude local oscillator/mixer circuit.

jr

edit add: the split chassis Philco sets early to mid 50s were pretty solid performers.

[DaveWM]

Germainum diode? heat sink when installed? Heat from a soldering iron will ruin a germainium diode if not heat sinked.

I would def input a composite video siganl at the grid of the 1st video amp just to clear everything beyond that. Make sure everything is isolated before doing this (a .1uf cap should do it, make sure there is no voltage between the grounds of of the chassis and the video comp ground. I generally use a meter to compare grounds before hooking ANY two things together. A DVD is a good source of a comp video (yellow rca jack). check the grounds 1st of ok hook dvd ground to chassis ground, then connect the center lead from the dvd comp video to thru the cap to the grid of the video amp. Its possible it could be out of phase (neg pic no sync) but most of the time it works.

If this produces a good pic then you know for sure its the RF/IF or a bad video detector diode.

I generally do a quick front to back ratio check on the detector diode in circuit IIRC it should be at least 4 to 1

[Davala]

Old coot..

Diode was backwards. Schematic through me off a bit, I put the black band of the diode matching the line on the diode on the schematic. Apparently that's not correct. So I reversed the diode and checked voltages. The 130b+ stayed steady regardless of signal. Hooked up and digital converter box and was met with no sync. Voltage was off on the plate of the 6BE6 sync tube. Wiggled it around and the voltage popped up and synch came in.

[Davala]

Vertical seemed off half frequency once I fixed the 6BE6 sync tube. Finally got a full image near the end of the range of the vert hold. I know I have some resistors to check as the vert linerarity is off quite a bit at the top. Tuner needs some tweaking too.

I'm very happy with the result so far. It can only get better. Got the original wooden stand for the TV I'm going to set up soon.

Thanks for all the help everybody!
Yay!
Matt Davala