Motorola ts907 low hv

[timmy]

Well those v1 v2 7-and 8 voltages are wrong and L4 and L5 shows they each have a .001 inside why couldn’t they be changed.

[timmy]

I looked inside there is ceramic caps in L4 L5 I would have to clip the ground to see if they are bad or shorted

[Yamamaya42]

Originally Posted by timmy

Well those v1 v2 7-and 8 voltages are wrong and L4 and L5 shows they each have a .001 inside why couldn’t they be changed.

as others have said, unlike changing resistors, changing capacitors in the IF section = 100% chance of needing to align the entire thing end to end, you would be better of replacing the 3w/2w power resistors, even if they seem OK, that are feeding power to the coils before even thinking of touching any caps in the area.

[timmy]

Originally Posted by Yamamaya42

as others have said, unlike changing resistors, changing capacitors in the IF section = 100% chance of needing to align the entire thing end to end, you would be better of replacing the 3w/2w power resistors, even if they seem OK, that are feeding power to the coils before even thinking of touching any caps in the area.

Well all I have to do is clip the ground on each cap it’s on the outside and I can then see if they are bad if they are then I’ll have to decide what to do after that. Those caps oscillate the coils correct ?

[Yamamaya42]

Originally Posted by timmy

I looked inside there is ceramic caps in L4 L5 I would have to clip the ground to see if they are bad or shorted

it be best not to disturb them yet, I would try fresh power resistors first.

if they are messed with, it will shift the alignment.

[Yamamaya42]

Originally Posted by timmy

Well all I have to do is clip the ground on each cap it’s on the outside and I can then see if they are bad if they are then I’ll have to decide what to do after that. Those caps oscillate the coils correct ?

they are part of an RC, circuit yes.

very delicate, the slightest touch can change it,

[timmy]

Originally Posted by Yamamaya42

it be best not to disturb them yet, I would try fresh power resistors first.

if they are messed with, it will shift the alignment.

I would think it’s not likely that both would go bad at the same time. These resistors are heavy wire wound I have never seen one of these rise in tolerance.

[Yamamaya42]

3w resistors are rather cheap now, and much smaller and run cooler than in the 60s, replacing them all won't cost much more than $10, and make SURE 100% that it's not a resistor problem, which is a good thing to do before looking at caps IMOH.

[timmy]

Same as the 2 .001 caps what’s the likelihood of both of those caps being bad. They are ceramics and I’m surprised that it wouldn’t be mica caps in such a circuit.

[Electronic M]

Ceramics almost never fail and when they do it's usually in sweep circuits where they're being whacked with several KV worth of pulses, not <300VDC and <3VAC that the IF subjects them to...

If you are concerned about the ceramic caps in the IF leaking current I gave you great advice before... Temporarily stick a cap 100X the capacitance in series. It will stop DC leakage and the series capacitance will be almost exactly the same as the original part alone.

[old_coot88]

The bulletproof-ness of ceramic caps is a fact. The only defective one I ever encountered was inside the motor of a cassette player. The complaint was sporadic overspeed. The motor had a 3-segment commutator, with 3 tiny ceramic caps bridging the gaps between segments. One of the caps was leaky, and replacing it cured the speed problem.

[Yamamaya42]

Since you stated that the voltages on pins 7-8 of the V1-V2 are wrong, but the 6EH7s are NOS, and the problem is not a bias 275v problem and extremely unlikely to be disc cap related, then once again the best path is to replace the power resistors, no matter how they seem to check out.

List here.
main power diodes
https://www.mouser.com/ProductDetail...2B4kkscA%3D%3D

6.8k 3w (r40, r49)
https://www.mouser.com/ProductDetail...0BKWoLFQ%3D%3D

2.7k 3w (r41, r50)
https://www.mouser.com/ProductDetail...Wwtn4Z2Q%3D%3D

8.2k 3w (r39 , r48 )
https://www.mouser.com/ProductDetail...2a7TUHog%3D%3D

Yes, use all 3w resistors, they will be smaller then the ones replaced, and much more reliable.
In fact replacing all resistors in the IF may be the only way to get it working again, and even then, you may not be able to.

[timmy]

When using the ohms chart for tube sockets use with tube in or out.

[Yamamaya42]

Originally Posted by timmy

When using the ohms chart for tube sockets use with tube in or out.

tubes in, but it does not really matter much, since only the heaters will alter the readings you may be taking, which will be low anyway, so if you do it tubes in via a test socket under the tube, or out, just probing socket alone, you should get same readings.

[timmy]

I’m getting a really bad reading on pin 8 of v1 should be 3200ohms 3.2k I’m getting 6.30k I figured I would check resistance on v1 and v2