Motorola ts907 low hv

[Yamamaya42]

The difference between ceramic disc capacitors and mica is easy to spot, a pic of the caps in question would help.

But do remember, if you ARE thinking of replacing the .001 disc capacitors, don't use any old caps, but be sure to get C0G (NP0) type, it will save you from a whole world of pain down the line.

[timmy]

Well I was not going to touch L5 cap seeing it works already and the questionable problem is in v1 L4 hopefully. All I can say at this point is the primary side of L4 has a red cap and the secondary side has a regular color disc cap and it’s so tucked in there tight I can’t even get a picture to show it. So I’ll try the secondary side cap first if it Works then great if not then I may have to take the coil out of the housing that it’s in.

[timmy]

I don’t even have a 1000pf mica I have micas that I can make up a 1000pf but then I have to leave it out of the coil housing don’t know if that’s acceptable or not.

[Yamamaya42]

Before doing anything to L4, you should try what others have suggested, V1 removed, and feed in the tuner subber into pin 7 the same as you did before, through a isolation capacitor, to see if you can get any signal through, you may have to adjust the gain on the subber a bit.

[timmy]

Originally Posted by Yamamaya42

Before doing anything to L4, you should try what others have suggested, V1 removed, and feed in the tuner subber into pin 7 the same as you did before, through a isolation capacitor, to see if you can get any signal through, you may have to adjust the gain on the subber a bit.

I had taken v1 pin2 off L3 and fed the subber in got the same as befor and with that wire off L3 I tried pin 7 but the tube was in and I got less of a response. When I fed v2 I used pin 2

[Yamamaya42]

possible choices.

https://www.mouser.com/ProductDetail...znO8lXZA%3D%3D
https://www.mouser.com/ProductDetail...dco7WMcA%3D%3D


Mica caps are NOT cheap!

[Yamamaya42]

It would most likely work better for you to put the original K1 couplet back in, as the 24meg section was not really that far off to matter that much to start with, and replacing it did not really do much.

[timmy]

Originally Posted by Yamamaya42

It would most likely work better for you to put the original K1 couplet back in, as the 24meg section was not really that far off to matter that much to start with, and replacing it did not really do much.

I already put the original k1 back in problem with it is the 2.2meg measured 2.4meg and the 2meg measured 2.4meg the 24meg measured 30meg and the 680k measured 740k this is why I made it up so I’ll leave it in for now and it may not be needed at all.

[Yamamaya42]

Originally Posted by timmy

I already put the original k1 back in problem with it is the 2.2meg measured 2.4meg and the 2meg measured 2.4meg the 24meg measured 30meg and the 680k measured 740k this is why I made it up so I’ll leave it in for now and it may not be needed at all.

https://www.allaboutcircuits.com/too...de-calculator/

that's all pretty much within 20% save for the 24 meg, which is just a hair.

most people say it's safe to let it go to 30%, then worry about it.
tube stuff is very forgiving with this!

[timmy]

I do have a 1000pf mica from the 1940s for test purposes it tests like new exactly 1.00

[Yamamaya42]

I would never trust it in a 60s type set, especially in the RF area, no idea what the voltage rating is, but it is a neat souvenir however!

[timmy]

Rather then use that old mica can modern micas be put in parallel to make the right capacitance. I know it’s the IF so it can be touchy.

[Yamamaya42]

Originally Posted by timmy

Rather then use that old mica can modern micas be put in parallel to make the right capacitance. I know it’s the IF so it can be touchy.

Doing that in an IF is not recommended...

the cap I pointed out IS the right capacitance, .001 @ 500v

598-CD19FD102JO3F mouser part #

[timmy]

So if the red cap that’s in L4 if it’s not a mica but rather a special type ceramic disc then replacing it with a mica should be better for the circuit.

[timmy]

Going to try 2 disc caps in v1 see what results I get if it works then when I get the mica cap then I’ll put it in. Regular disc cap should work in place of a mica if that’s infact what’s in there hopefully I get a good result.