#16
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thats about 15 min from me. hope you had a good time. I get up to VA now and then, near DC (centreville)for work.
fingers crossed should be getting the vert output today.... |
#17
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got it
now about hooking it up, I guess the smart thing to do would be to make sure I have the exact same wire colors before doing anything. Make sure the match up to the schematic cut them off the bad xformer fairly close to the xformr so I can use them for lead dress examples when I replace with the new. does that seem reasonable? never had to replace a tranny before. |
#18
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Yeah I'd cut them close to the tranny, too. Sometimes they give you just barely enough to work with.
Keeping our fingers cross!
__________________
Charlie Trahan He who dies with the most toys still dies. |
#19
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the plan is to spend some quality time on it tonight, prelim checks show the new one is not shorted so I am pretty sure I have a correct diagnosis.
I wonder if it spontaniously shorted or if there was some defect in the vert circuit thay could have caused a short.... if that was to happen I assume there would have been a spike in current. I think i will double check the vert output tube before firing it up. look for shorts etc... |
#20
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hmmm looks like that short 9 pin fat tube is the vert output. It is the one with the leaky 50uf cap (replaced it) if that was a cathode bypass, then the leak may have reduced the bias and caused the tube to pull too much current thru the load (primary of the vert trans) of course I dont think I have the right tube tester for THAT tube
yep thats it a 6GF7 dual triode, and that was a cathod bypass cap. Oh well, I can wire it up, but I think I will hold off power up until I can get that tube checked for shorts, prob ok but I jsut would hate to toast the new tranny. Last edited by DaveWM; 10-22-2009 at 04:16 PM. |
Audiokarma |
#21
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sams and RCA service man both show about -55v bias on the vert osc output grid, of course they show diff voltages for the grid and cathode but both net to about -55.
The sams shows a 38ma current thru the cathode, no way to read that directly but I guess I could determine it based on the V drop across the cathode resistor.. hmmm scratch that not that simple, I was reading something wrong. This would be a nice time to have a test socket that you could jumper each pin on or off. not a tube extender but a tube extender that you could make/break the pins for current readings. I dont know if such a think exist. Last edited by DaveWM; 10-22-2009 at 04:38 PM. |
#22
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Make sure you check the vertical center control. I have seen them short to chassis ground and burn out transformers and the power supply.
Ed |
#23
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I will check that thanks.
well it went fine, tranny in, did a slow power up on the variac with the vert and horz tubes pulled. got up to about 250ma I think the sams says about 400ma but of course I did not have the horz/vert operating. The cans stayed cold so hope that is all good. Will check that vert center pot (did the power up before reading that post). one odd thing there were two color coded wires that went to the convergence plug that were not "right" the schematic called for Grn Red pin 5 .8 ohm Blk Grn ground Blk red pin 4 1.5 ohm blk grn is the center tap of the other two. the resistance measurements did not jive I had to reverse the pin 5 and pin 4 connections. I confirmed the resistance measurements against the old tranny. on it the color code matched the schematic and the resistance measurements matched. any way if for some reason I have issues I have enough slack to reconnect per color code (I even left a small tail of the old wire on the socket pin to know which ones were installed different from the code). there was a single .001 2000v ceramic tube cap off the primary plate side of the tranny to ground, My cap tester only goes to 450v so I could not test for leakage at rated volts. I had a couple .002 3kv disk caps I put in series and used them. I will go ahead and get the proper cap for it. the plan now is to take it to a local shop with a good tester and check all the tubes out. |
#24
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checked the vert cent pot, all leads to ground are about 7k which is the same as the B+ load so that looks ok. Thanks for the heads up.
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#25
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Quote:
I really like the cabinet and it has a swivel base. This set had a shorted vert cent pot and it damaged the power supply. I was lucky that it did not take out the power transformer but had to replace all the can caps, B + Diodes, Power switch and the circuit breaker. The person I bought the set from HAD to plug it in and turn it on. Ed |
Audiokarma |
#26
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nice cabinet, I am going to have to make a cabinet for my the old one is still wrapped up, termites are contained (i hope) but the damage is severe.
right now I am leaning toward a simple ply box with veneers and maybe some nice thin med long legs (the kind that screw on, nice if I can find some with a brass lower half). I sure would like to reproduce something nice like yours but my wood working is limited. what do you think about the color code problem on that one section? ever run into something like that? Last edited by DaveWM; 10-23-2009 at 07:33 AM. |
#27
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TMA96 info
Here's what my manual has for the TMA96 - hope it helps with the tuner woes.
Cheers,
__________________
Brian USN RET (Avionics / Cal) CET- Consumer Repair and Avionics ('88) "Capacitor Cosmetologist since '79" When fuses go to work, they quit! |
#28
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I'll try this again.
__________________
Brian USN RET (Avionics / Cal) CET- Consumer Repair and Avionics ('88) "Capacitor Cosmetologist since '79" When fuses go to work, they quit! Last edited by Findm-Keepm; 01-03-2017 at 08:20 AM. |
#29
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got it thx, it sitting on the variac all tubes out for a slow reform.
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#30
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Wow, Ed! That's a nice looking 16!
I had one similar a few years back, but the top of the cabinet was in pretty bad shape due to getting wet for a very long time. It was a remote set. I gave it to Rich since he was tinkering with rebuilding cabinets back then.
__________________
Charlie Trahan He who dies with the most toys still dies. |
Audiokarma |
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