Hi all, Good news, this project is coming to an end....It's nearly done.
Over the past few months I've been slowly picking away at it, replacing components here and there, haven't had much time to really spend on it only in the past few weeks has some real progress been made.
Every single paper and electrolytic capacitor has been replaced along with several resistors in which some were way out of tolerance, others were ok but decided to replace anyway for peace of mind. Replaced the rectifier diodes and the screened cable going from the tuner to the 1st IF as the orignal was all stiff and no doubt its dielectric properties would have gone a long time ago.
Fitting some of the new electroytics, I had to compromise as to where to put them as the originals were buried in places and restuffing the original cans, I wasn't even going to go there but managed to put the new ones in various places so it still looks tidy. I had to mount some on a tag strip as the area would not allow me to put the new ones in place as they would have been right above the B+ droppers and in amongst other components.
I did though encounter a couple of faults which had to be sorted, the first one was width related. From cold the width was fine and the control could be adjusted to suit, after about 5-10 minutes the width would increase in size and get to a point where it was too much and it was affecting the boost voltage and the control had to be turned hard to one end which I didn't like so I set out find out what was causing the issue.
In the end it was width control pot, obviously heat and voltage was causing the resistance to change after time. Luckily the pot on the donor chassis was ok, so I put it in and now the width and boost voltage are stable - phew!
The other problem kind of led me on a wild goose chase in a way, again it was a resistor causing the problem, after about 1/2 hour I noticed the contrast would reduce and picture would get a bit washed out and I had to adjust the AGC control to compensate as it warmed but even hard at one end it wasn't good enough.
I started with the tuner and did find a 5.6k inside which has risen to about 20K, but that didn't fix it so started poking around with the scope and confirmed that it wasn't the front end causing the problem. Next I moved to looking around the AGC gate/sync area and eventually found a 22k resistor that was heat sensitive, spraying it with freeze would restore the contrast to normal but something interesting is that while it was faulting, touching anything around there with meter probes would boost the contrast level, but after the new resistor was put in, this had very little or no effect, must have the capacitance of the meter probes compensating for the fault!
This one did take a while to find in between getting constantly interupted while in the middle of it all, but got there in the end!
So there we have it, too queer faults both caused by resistors this time, not capactiors for a change!
At this point in time all I have to do now is make up a lead/plug for the speaker and output transformer and put that and chassis back in the cabinet.
I have decided to leave the chassis surface alone as it had originally been sprayed with silver paint and don't want to disturb it by cleaning. You can see it starting to flake off in places but it isn't not going to rust away. I might just give the chassis top a light spray with some silicone anyway.
So all going well the next update should be of the set all back together and playing.
Attached are recent photos and the final pile of dead bits.
Stay tuned...
Cheers
Glen