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Old 14th Oct 2020, 9:53 pm   #41
Skywave
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Arrow Re: Advance type 63A

Quote:
Originally Posted by WaveyDipole View Post
Anyone know what size knobs fit this sig gen please? None of my knobs for 6.3mm shafts seems to fit. These seems to be fractionally bigger in diameter.
On account of the age of this item, the shafts for the controls will almost certainly be of 0.25" diameter.
0.25" equals 6.35 mm. Hence, a metric-type knob for a shaft of 6.30 mm. will have a hole that is too small for a 0.25" dia. shaft.

Re: posts #35 & #36: alignment of scale to correspond with the actual frequency output. ISTR that with mine I followed the classical approach of adjusting the inductor at the LF end and the capacitance at the HF end, per band.
I've always understood that the essential reasoning behind that approach is that to take into account stray reactance, stray C is more predominant at the HF end whereas stray L is similarly predominant at the LF end.

I have an Advance type 63 here: about 12 months ago I did a renovation. If the notes & photos I made during that work will be any help, let me know.

Al.

Last edited by Skywave; 14th Oct 2020 at 10:05 pm. Reason: Insert para. 2
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Old 15th Oct 2020, 6:45 pm   #42
WaveyDipole
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Default Re: Advance type 63A

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Originally Posted by OldTechFan96 View Post
I noticed that the service manual for the Advance SG63E includes instructions for a full RF alignment.

Pages 8 and 9. The instructions probably can be adapted for your Advance 63A, WD.
Thank you. I will review that information.

Quote:
Originally Posted by Skywave View Post
Quote:
Originally Posted by WaveyDipole View Post
Anyone know what size knobs fit this sig gen please? None of my knobs for 6.3mm shafts seems to fit. These seems to be fractionally bigger in diameter.
On account of the age of this item, the shafts for the controls will almost certainly be of 0.25" diameter.
0.25" equals 6.35 mm. Hence, a metric-type knob for a shaft of 6.30 mm. will have a hole that is too small for a 0.25" dia. shaft.
That would explain it then. The shaft diameter is definitely too big for 6.3mm knobs but only slightly. I was hoping they would fit 6.4mm knobs although these seem to be a little more difficult to come by. There are some examples on eBay though. Not cheap to get a whole matching set!

Quote:
Originally Posted by Skywave View Post
Re: posts #35 & #36: alignment of scale to correspond with the actual frequency output. ISTR that with mine I followed the classical approach of adjusting the inductor at the LF end and the capacitance at the HF end, per band.
I've always understood that the essential reasoning behind that approach is that to take into account stray reactance, stray C is more predominant at the HF end whereas stray L is similarly predominant at the LF end.

I have an Advance type 63 here: about 12 months ago I did a renovation. If the notes & photos I made during that work will be any help, let me know.

Al.
Thank you. That is useful to understand. The adjustment seems to be a just a tuned LC circuit for each range and adjusting either L or C simply changes the resonant frequency moving the whole range up and down the scale. I was wondering whether there was a preferred method of adjustment. Unless I am missing something, it doesn't seem like a radio where you tune/match the frequency to a point at each end of the scale.

Thank you for the offer of your notes. If you have a paragraph or two specifically on how the tuning/alignment was done I would certainly be interested.
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Old 18th Nov 2020, 2:55 pm   #43
WaveyDipole
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Default Re: Advance type 63A

I was finally able to spend some time today tuning the oscillator up. It was useful to have both the frequency counter display and the crystal earpiece connected to monitor the crystal heterodynes. First the dial adjustment was centred and the instrument allowed to warm up for 30min or so.

Adjustments were made to the coil first at the low end, then the capacitor trimmer at the top end. To achieve the best accuracy, several iterations were required for each range, moving from one end of the scale to the other and checking both end and mid-points. Each range had to be checked and adjusted in this manner which which required a bit of patience! It is worth noting that the coil formers have two coils on them each. The upper coils correspond to SW1/B and have a capacitor in parallel to form a tuned circuit. The lower coils correspond to SW1/A. The slug for ranges 2 - 5 has to be engaged with the lower coil. For range 1, the slug is in the top of the former. The exception is the highest frequency range where, rather than a slug inside a coil, a metallic strip needs to be bent to make the loop wider or narrower. With a bit of a careful fiddle it was eventually adjusted to give a reading of 100.02MHz on the 100MHz mark which was close enough. The high end adjustment is mounted on the back of the large variable capacitor.

All adjustments were made so that the far ends of the scale were as close as possible to the frequency counter reading and confirming with the crystal beat note where possible. Mid-points were then also checked for accuracy across the range. The specifications for both the 63 (non A) and 63E are quoted as being ±1% and it was possible to achieve an adjustment where everything was well within 1% of the expected value without any need to adjust the scale, so I am happy with that for the 63A. The scale does not track entirely accurately - which is to be expected - but still manages to stay within 1% without needing any adjustment.

All that is required now is to put the covers back on and possibly find a way to manufacture that crystal calibrator probe connector.

Last edited by WaveyDipole; 18th Nov 2020 at 3:15 pm.
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