[Milsurplus] Racal 17L - missing tuning hiss on Mc dial

[francesco.sartorello at virgilio.it]

Hello guys,

I am spending a lot of time in restoring a really nice RA17L, which worked
very well something like twenty years ago.

I took all the obvious steps, checked  and replaced tubes, checked all
voltages and resistance, replaced all paper caps and most of micas, and I
have now a radio which works perfectly on bands 0 and 1, with a dramatic
loss of sensitivity higher up.

I think problem lies in the 37.5 Mc  amplifier chain and mostly in the BP
Filter, because at TP3, while doing test in accordance to the manual, I
measure mVolts, not 3-5 V as expected.

Is this the reason why I miss the tuning hiss on Mc dial?

All other circuits ( front end, vfo 1, vfo 2, harmonic generator,  all 3
mixers, 100kc filters and chain)work perfectly, controlled with extensive
instrumentation, I just miss the 37.5 signal to the 2nd mixer.

Vintage radio forum in UK addressed repeatedly this issue which seems a
major cause for loss of sensitivity: no suggestion worked on my radio.

Is there anyone in this group still proficient on this beast, or would you
be so kind to address me to the correct resources?

All the best!

Francesco Sartorello

(Former  i1SFT, 390A, SP600, all Collins gear, all German and US WWII gear,
.)   



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