Rca ta 129b

[bandersen]

Thanks for the update. I only had 600v black wire when I started working on TVs in earnest. I ended up ordering a rainbow assortment from radiodaze.

I'm surprised you found so many bad tubes. Are they total dead or weak ?

Early RCA sets used some pretty hefty dividers/bleeders. Check out this one from Phil's site: http://www.antiqueradio.org/art/RCA630TS18.jpg

Good luck. Can't wait to see it spring to life.

[pugs5061]

A few more details on the tubes:
V2-6AG5-Mixer-showed a short
V8-6AL5-Sync limiter-Questionable 48 out of 100
V9-12AU7-Video Amp-Questionable 54 out of 100
V13-6AV6-AF Amp-Bad-30 out of 100
V14-6V6GT-Audio Output-Had a bad 6K6GT installed instead-10 out of 100 *Did this cause major problems?
V18-6K6GT-Vert. Output-Questionable 48 out of 100

Radio Tubes
V26-6J6-Shorted
V27-6BA6-Bad-30 out of 100
V29-6BF6-Shorted
V30-Wrong Tube-6AL5 installed instead of 6AU6 (6AL5 did test ok)

I personally think before I bought this set but after it was put out to pasture someone tried to replace tubes and used the wrong ones and created even more problems. I'm a newbie though anyone elses opinion would be valued!

Anyways I think I will test most of the coils for resistance after I'm done with the resistors. Something shorted those tubes. I'll start in there respected circuits.

I ordered most of the tubes through Antique Electrical Supply today. No harm, only like $40 for 12 new tubes. The 2 I didn't order: A 12AU7 and a 6SN7GT, (I didn't list it but one was only in the mid 60's and there were like 4 more so I thought it might be a good idea to have an extra), I bid on on ebay. I won 2 auctions: 2 untested 12AU7's for $4 and 2 untested 6SN7GT's for $.99. I'll see how lucky I am but buying them for the kind of price they want retail seemed crazy.

[pugs5061]

Well I put power to the set yesterday. I'm getting way to much AC and not enough DC right out of the box. Pins 2 and 8 of my 5U4's are supposed to have 225VDC. Getting varying voltages voltages as I mess with things and change out more resistors but I have 40VDC now. I figure something is messed up in my electrolytes, you know a newbie mistake. Only other options I can see are transformer or focus coil problems. I'm still thinking I'm to blame though with the capacitors. I will post more if I can't figure it out.

[pugs5061]

Update after a few hours working on the set. AC is fine on the 5U4's but pins 2 and 8 still show low DC. The voltage behind (negative side) my electrolytes is still too high even after finding 1 mistake (put a 470k resistor in front of C2 instead of behind!). I checked everything but the high voltage (Didn't really want too!) and every other tube pin looks good! I thought I had a problem with the CRT too but I worked through that too (Rejuvenated on high with a B & K 445! Wish I had a newer B & K!). The only other problem I've had are the stupid resistors imbedded in the chassis of this RCA chassis. Has anyone else had those resistors go bad? Why did they do it? Going to sleep now but I figure it is still a dumbass mistake by me on the electrolytes or something really bad in the High Voltage(never really checked it out). It smells real close! when I get a picture(or Rastor of somesort) you get a picture!

[bandersen]

Hang in there and don't rush anything! We're all rooting for ya.

[pugs5061]

The main power supply problems seem to be fixed. I didn't know what I did but I would imagine I just pushed a wire away from another. The resistance on the 5U4 pins 2 and 8 jumped from 60 ohms to 5.5K where it was supposed to be. The radio now works, AM sounds great, FM sounds like it is underwater, may need an alignment. No raster yet but as I powered up I remembered the pot that I had circumvented with a resistor. That may be the cause. I am worried about my tuner though. Having never seen an old set in years, I figured it was normal for the tuner to spin like on a radio. No click, click to turn channels. I now think I may have to go in and investigate. I think I should get a raster with a bad tuner right? Anyways moving forward.

[bandersen]

Yeah, you should have a raster regardless of the tuner. Do you have sound from the TV ?

Maybe you have the same tuner click problem as pielock373 did ? (scroll down to the bottom).

[pugs5061]

I didn't spend much time on the set today. Forward progress after a couple setbacks but thats the breaks. Power problem came back but that was actually a good thing because I figured exactly where the problem was and was able to fix it for good. It was in an area where I had not touched anything, just a wire that had to be resoldered.
I think the reason I have no raster starts with excess voltage and not enough resistance on pin 1 of my Horizontal output tube (6BG6G). This isn't the reason for no raster but just the end result of something else in this circuit being messed up. There is a switch called a Horizontal Drive that feeds parts of this tube, resistance wise everything in the area seems messed up. I also saw that there is a big resistor of 500 ohms 20 watts feeding this circuit also. It reads 50 ohms. I will replace everything in sight around the drive, hopefully the big resistor is available at the local electronics shop. I'm probably SOL on the drive itself for now. I will also replace every cap and resitor in sight not replaced yet including the old Mica's. If I get the parts I should get it in shape in another day or so.

[bandersen]

Hmm - I'm not sure what you mean by a switch. Horizontal Drive should be a variable capacitor used to set the amount of 'drive' going to the HOT (6BG6). Are you sure it's a switch and not an adjustable control ?

I'd leave the micas alone until you eliminated all other possibilities. They generally don't go bad (seem to be more lately though) and can be tough to find correct replacements for. The ones around the HOT can be rated for 1,000 volts or more.

[pugs5061]

Yes, Its a variable capacitor, the schematic called it a drive. Anyways I think you were right, I only replaced one of the Micas(560pf) with 2 270pf's in paralell but after staring at the circuit a while I realized the switch for my width control(optional) was hooked in through this pin and there can't be infinite resistance as shown on the specifications. The width control switch is shown elsewhere on the schematics in between the dotted lines. Anyways I went ahead and tore into the HV being that I thought my resisistances were good. I found one hell of a bad wire short to the chassis thats probably been there for years. I replaced that, checked out the rest of the flyback, rechecked Hrz output, Hrz Oscilator, Damper and HV Rectifier tubes all OK. Then I checked Resistances on the damper and Oscilator sockets and everything looked good. I also checked resistances on the flyback wires and found very little resistance between them but no shorts, is that normal(all less than 10 ohms between them)? I then went ahead and powered up. I could hear the high pitched squeal of the horizontal? Or is it vertical? Started playing with the brightness pot and poof, smoke from the flyback area. One question I have is how those pots are typically wired. There are 3 terminals. I had a resistor going to center and a wire going to the second. The terminal with the wire broke off. I reconnected the wire to the opposite side. The resistances matched. Could this have caused this? Anyways it looks as though I caught everything in time no harm that I can tell. I plan on going through everything again focusing on the oscilator because there are so many resisters in this circuit and it just doesn't look right.

[bandersen]

The squeal was probably from the horizontal (around 15.75 KHz). That smoke came from something - hopefully just a resistor. The HOT might have been getting too much drive and smoked one. Is your set fused ? If so, did the fuse blow ?

Generally, you could swap a wire from one end of a pot to the other, unused end. Of course, the control would work backwards then.

Could you scan or take a picture of that area of the schematic and post it ?

[pugs5061]

Thats what I thought with the pot. It will work backwards though. Thanx.
I have checked most of the set out and I did find a few resistors that I know were fine before, that I had to replace. I took apart the tuner cleaned everything up, replaced resistors and left the clicker ball alone. Yes it is the same as Pielocks (same problem too) but I figured that I wanted to get the set up and going first. Besides as long as channel 3 works I'll be happy for a while until the cabinet is complete. I have one problem I have been fighting since before I powered up. I'm sure its just a good old fashion short somewhere materializing in the Vertical output tube. I'm pretty sure this is what caused the smoke. If I get too frustrated I will download everything needed for help but for now I am going to keep going it alone sort of speak. Thank you for the offers of help and I'm sure I will need them sooner or later but as long as I am still enjoying myself and not so frustrated I want to put my head through a wall, I'll be fine.

[pugs5061]

Also, yes the set is fused and the fuse did not blow. 1/4 amp I believe.

[pugs5061]

Found my problem. The vertical Blocking Osc. Transformer (T2) is showing infinite resistance. It wasn't completely infinite until I started wiggling wires and saw how irratic my resistances throughout were. The wires were all crumbly and basically gone and I hoped the problem may be just outside the transformer and I thought maybe I could just pull it out and resolder exterior wires if I was lucky. I'm actually even luckier than that though! I found a NOS transformer. Inexpensive too! Done working on this until I get the part or I find out I can't get it. (Waiting for confirmation now). Out of time now but I will post the schematic along with what I figured happened in the next day or so.

[pugs5061]

Transformer is on its way!