Hi guys,
I just got this TV off of CL. I have a friend to check out the 7JP4 crt. I have an ad in the classifieds for some knobs. I'm aware of the HV fade problem. But for $15 I couldn't refuse.
I have to order a bunch of caps and resistors. The "Bumble Bee", the E-Caps, and tubular caps are no problem. There are some that look like "hot dogs", and some that look like domino's. If I have to replace a Hot Dog cap what would I use. They are mostly from 2.2pf to 1500pf. The domino caps look like they are Mica but some could be paper. How do I tell the difference. I'm including pics and a schematic of the TV.
C54 is the only one that really needs replacing as it is a molded paper cap.
The "hot dogs" are tubular ceramics and are usually high grade (NPO) and very reliable. These are typically in RF circuits and better left as is.
The remaining ones in the photos are molded micas which should be fine. To the left of C78 is a molded ceramic cap which looks like a resistor (but with a different color code). These should also be left alone. Replacing these will upset the alignment.
(This post was last modified: 03-25-2016, 06:18 PM by Mondial.)
Nice find! That chassis looks decent. A simple electrostatic deflected set. Take your time in the rebuild and do a section at a time, starting with the power supply electrolytics. Generally you can tell your mica caps by the smaller values, in PF, MMF, uuF or something similar, your paper caps are larger (.01, .001 mf, mfd, uf, and such). Can be a little confusing at first since some of those look like micas. The black striped 'bumble bee' caps are also paper caps and should be replaced. You can take them out and sell them on Ebay $$$ I hope you can find a set of knobs, or something that will look correct anyway. Keep us up on the progress.
If I could find the place called "Somewhere", I could find "Anything"
Tim
Jesus cried out and said, "Whoever believes in me , believes not in me but in him who sent me" John 12:44
Thanks guys on the comments. Very helpful. I'll use a film cap for the .01uf and the 3 others will be micas. I'll keep ya posted. Anybody got any knobs?
I'm getting to know the chassis. I'm studying the schematics and parts layout. What I like to do is to mark each component with a little piece of masking tape the Item number from the parts list. I did all the Bumble Bee, paper, and square mica caps, the high voltage circuit resistors, the high wattage resistors, and high value resistors for now.
I enter the resistor and capacitor parts lists into Excel. Then I can sort them and it helps me come up with a replacement parts list that I need to order.
While doing that I came across a connection that wasn't soldered! The lead from the resistor just pulled up from the pin on the tube socket. While there was ample solder on the tube pin, the resistor was missed in that it never got a good solder joint.
I think I have a later run for this chassis. My Sams 140-7 shows the components, but I have more terminal strips and slightly different locations for some of the components. So far I've found all the components that I've been looking for. Yes, some of those pesky 1/2W carbon comp resistors can hide very well, very well indeed. Some of the paper caps shown in the Sams are Bumble Bee caps in mine.
After spending some time looking over this chassis I think everything is original. Nothing has been changed except for a few tubes. The picture tube is a Philco too.
Sweet set ! You are lucky it is unmolested. It'll make things a lot easier. I really like your photos. They make following your work MUCH easier. Keep up the good work !
(03-27-2016, 04:33 PM)mikethedruid Wrote: Sweet set ! You are lucky it is unmolested. It'll make things a lot easier. I really like your photos. They make following your work MUCH easier. Keep up the good work !
Thanks Mike. Pictures make the thread a lot more interesting.
Nice set Crist! I have the same chassis in a bakelite cabinet and the resto went very smoothly. I found a fair number of resistors out of tolerance and the big sand resistor had an open section. I have never had a fading issue with mine and I have watched it for a couple of hours at a time. It makes a really nice picture.
(03-28-2016, 12:25 AM)gregb Wrote: Nice set Crist! I have the same chassis in a bakelite cabinet and the resto went very smoothly. I found a fair number of resistors out of tolerance and the big sand resistor had an open section. I have never had a fading issue with mine and I have watched it for a couple of hours at a time. It makes a really nice picture.
Gregb
Greg,
That's good news on the HV fade!
I'm going to get the CRT tested tomorrow in a working set. I hope it checks out good! If it does, then I'll order caps, resistors, and the like.
Would it be possible to email me some hi-res pics of your chassis? Both top side and underneath. I'd like to see an example of how one was done. This is my first TV. I've done several radios and cabinets before.
Still need those knobs! Anybody?
Thanks.
Crist
(This post was last modified: 03-28-2016, 09:29 PM by Crist Rigotti.)
Sorry Crist, I didn't take any pictures while working on it. I just bought a new camera and will be documenting things I work on from this point forward.
I hope you can find a set of knobs, or something that will look correct anyway. Keep us up on the progress.
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