wow, very little current!, I will try to find these little tubes. I am going to California and Arizona tomorrow, I might be lucky there. thank you.

the tubedepot has them and also the 5246 on ebay, great help thank you!!

Keep in mind that the 5642 is likely not a direct replacement for the 1DK1... I mentioned them as an illustration of a similar tube that is rated for very low current. I can't find a data sheet for the 1DK1.

jr

thank you, I realize that, I went ahead and purchased a few 1dk1 from tubedepot.
hope they will arrive, I live in italy and many of my packages get lost in the post!!!!.

Hi, back from the US with tube rectifiers, I installed them and yes, I have HV now a lot more stable and a raster. lum is not great but could be normal on this little set. the transistor still gets really hot but seems to be taking the heat with no problem, this now showed me the next problem. I have a vertical issue, I have a straight line on top of the screen and to final stage transistor is dead cold. none of the controls have an effect although on the scope I see some variations when I move them. I might have an open resistor of an ope transistor if that is possible. when I disconnect the yoke, the line goes in the middle of the screen. will work again on it today.
good weekend to all

Shorted 500uf/12volt capacitor between the emitter of the vertical output transistor and the deflection yoke? :scratch2:

jt

Hi, I replaced all the capacitors on the board with new ones, then just replaced the 500uf again, now I have the top half of the screen lit. getting somewhere!!!, I ordered some new transistors to replace the 2sb147. I measured it but being a Ge, it measures funny and still don't know if it is good or not.
I never thought a transistor could go weak but after having replaced the one in the horiz, I had much better results with the HV and raster!?!?. I might have the same issue with the vert output transistor. They are all Ge transistor, perhaps being Ge they can go weak. would it be the case?

There are several failure modes that can weaken a transistor....I have read that there are sometimes multiple connections to the chip that are very fine gold wires, failure of one or more can weaken the performance, but the transistor will still function somewhat.
Junction leakage current can also increase with age.
Rare, but not unknown problems.

jr

Only Ge fails I remember were dead short, open or intermittent
open, & noisy ( crackling in audio). Not like Si that work or dont.
Glad Ge transistors are long gone !

For overheating HOT measure the current. SAMS schematics almost
always give the specs, someone here will help with that. You can
have a problem that does not show in the picture especially on such
an aged set.
Ge's often use complex bias with diodes & thermistors. Can be quite
hard to find problems when something is only "a little off".

Good luck
Zeno:smoke:
LFOD !

well, learning everyday!!!, not used to the Ge but they seem to take more stress than the usual Si.
I have another question, in the Horiz osc. what are the elements that decide for the frequency, I realized that it never reaches 15750 Hertz, instead, it goes extremely low (below 5kHz) making the whole circuit noisy (scary!!) and the highest frequencies I can reach in 11 to 12 kHz.
I was misled by the sams doc showing only half the frequency but at the output of the
2sc41 I surely need 15750 Hz or close to this. Am I wrong???.
I measured all elements and they are within specs unless there is a mistake in the doc.

this set is a real challenge.
thank you again for all the tips

You are measuring frequency with an oscilloscope, and not a counter correct? Counters can be VERY inaccurate on non-sinusoidal waveforms (which is what a sweep sawtooth is).

yes, I am measuring it with an oscilloscope that has a frequency counter. you are right, any kind on interference or spike will change the count.
I just read the "How important is this cap's value (Sony 8-301W)? " in this forum and learnt quite a few things on the oscillator. I will go ahead and replace the caps 98 to 101 and try to adjust L14 but still need to figure out a way to do it.
Is L13 a critical one?
thank you

Hi,

I work again on the set and measured all caps and the are spot on, only one, C98 was 10% higher than expected, still decent. I tried to tune B1 in L14 but with only little effect, max frequency 12.3kHz. I then changed C101 to 10nF instead of 20, frequency went up to 14.5kHz, changed it again to 5nF and now I have a very decent range going from 14k to way over 16kHz. The pulse at the horiz. output X20 is now very clean and steady. (before I could see some unwanted spikes). I applied a signal and I could sync it but kinda wobbly, not stable. I adjusted the horiz drive and it somehow improved it but still not OK.
I don't know if the coil L14 could be bad, if it is the case, I could take it from another set and try it. I am a bit concerned by the big difference in C101 to make work.
With C101 changed, do I also need to change C99/C100. I think C98 is outside and does not influence the frequency.
Getting somewhere!!!!
with a signal applied, it is also rather noisy. but this will be the next problem.

Perhaps the diode following the coil is bad? :scratch2:

jr