Back to the VT-71H

[timmy]

Originally Posted by bandersen

Well there's your problem. That's the wrong ballast for this revision. Switch pins 6 and 5

Put 5 in 6 position?

[timmy]

Originally Posted by bandersen

Also 150 ohms is a bit too much. 120 would be better

My other motos use the same ohms and they work perfectly so I’ll see lol

[Yamamaya42]

Originally Posted by Chris K

This is what I did as per Bob’s instructions. These are his photos. The only change I made was switching the CL-90 lead from pin 6 to pin 5.

so, power comes in from interlock, to pin 6, to CL-90, resistors (3) and onward?
things are a bit confused :p

[timmy]

This is getting really bizarre I switched 5-6 tubes light but the b+ having the meter on + - the voltage starts to go up then drops showing I have the polarity wrong on the meter and no b+ the 2 150 ohm resistors get hot but the others stay cold I had checked the supply caps and they look correct for wiring. This is nuts because I believe this may be the problem with the clipper circuit not enough voltage.

[Chris K]

Yeah I’m lost as to where we are with this. I think we need to call in Chicago to straighten us out. The way I understood the thread exchange many pages ago, the TS-4H has a slightly different pin arrangement for the ballast. If u look at the picture I posted of Bobs hand drawn schematic, what I understood at the time was for the H chassis a switch of the CL-90 needed to go to pin 5 and not pin 6 as it was drawn. Given all the recent confusion I think we probably need to get back to basics as to what the ballast should look like.

[bandersen]

That is the only change required. Move anything from pin 6 to 5. Done

[timmy]

I don’t want to look at the ballast that you made what I’m trying to do is put it as it was original with resistors in the ballast because maybe I’m missing something in the power supply link I don’t know yet. So now the ballast is right and now no b+ and the Polaris showing it’s wrong if so the diodes won’t work.

[timmy]

So now checking the pins how I wired the ballast with 5-6 switched the other resistors can’t be checked according to the pins because one for each resistor was moved except for the heater resistors that’s good I wired the ballast from the schematic 4 resistors in that order.

[Chris K]

Originally Posted by bandersen

That is the only change required. Move anything from pin 6 to 5. Done

Bob…what diodes did you use to replace the selenium rectifiers? I would normally do this with 1N4007 diodes but I vaguely recall a suggestion, not necessarily from you, to use something else. When I spoke to Tim he believed the rectifier diodes I i installed were too big to be 007s.

[timmy]

Ok alarms off the ballast worked but I’m getting the same voltage as with the new ballast so Chris your ballast is ok so now there are only 4 places that take b+ 2 for the clipper 1 for the audio trans and 1 for the limiter so I will be looking at the clipper first because of what the screen is showing maybe the clipper tube is full on drawing down the b+ it’s been as low as 107v but the b++ is still around 280v the sound is good almost to say the audio trans is good. Chris the diodes you have here are good 1kv 3 amp. The horizontal is working but there is very limited vertical because the vertical hold don’t work at all I’ll be checking the pot and there are a few caps in the vertical that could be the cause here as I had to replace them in a few of of my sets. If you look at when the pic rolls slow there is a block separating top from bottom that moves as it rolls but it’s stuck just below the center of the screen won’t move with the pot.

[Chris K]

I have a parts chassis. I can send the pot to u

[timmy]

Originally Posted by Chris K

I have a parts chassis. I can send the pot to u

I’m going to check the pot tomorrow it’s a 5 meg I have one here if need be. Just got to get to the bottom of these issues and didn’t know of any of these problems until video was present which helps. Originally when video first came on shortly after I heard a hi voltage arc from where i don’t know but that’s when all the vertical issues started.

[Yamamaya42]

Originally Posted by Chris K

Bob…what diodes did you use to replace the selenium rectifiers? I would normally do this with 1N4007 diodes but I vaguely recall a suggestion, not necessarily from you, to use something else. When I spoke to Tim he believed the rectifier diodes I i installed were too big to be 007s.

Due the general knowledge that a selenium rectifier is not as efficient as the replacement silicon diode, where the OEM selenium may drop anywhere between 5 and 20 Volts (or more) when new, and slowly increase as the part ages, a silicon diode has a drop of less than .6 Volts, give or take, resulting in substantially higher bias voltages, which need to be often adjusted for with a dropping resistor.
As for what kind of silicon diode to use, there is a large amount of flexibility as long as PIV & current needs are met, so as Timmy mentioned, the 1000v 3a ones used are pretty much bullet proof in such a set that hardly takes 1 amp.

[timmy]

Well oddly if I turn the fine tune alittle bit the picture straightens out and the vertical hold works so I’m wondering now if the signal is overloading , the pic is not perfectly clear but watchable.

[bandersen]

I used 1N5408 1,000 volt, 3 Amp diodes. There's no need to add additional resistance. That's already taken care of inside the ballast by the thermistor and surge suppression resistances. I've found the resulting B++ to be around 230 volts in working sets.