[R-390] Fwd: Fwd: RF Module Adjustable Slug Seperated from Adjusting Screw

[Paul Dulaff]

----- Forwarded Message -----
From: Paul Dulaff <pdulaff at embarqmail.com>
To: r-390-bounces at mailman.qth.net
Sent: Tue, 17 May 2011 14:13:22 -0400 (EDT)
Subject: Fwd: [R-390] RF Module Adjustable Slug Seperated from Adjusting Screw

Everyone

Got several responses to the question regarding the slug problem. Just after I wrote the e-mail to the list, I went ahead and soldered the spring shaft to the inside of the adjuster screw. Looking at the slug assembly carefully, this is how it was manufactured in the first place. This agreed with the responses I later received. It appears that the solder connection had a fatigue failure after 56 years.

I found 2 other slugs in the same condition and repaired them the same way. I did a quick alignment of all affected sections with success. Rig is now working on all bands. All the heterodyne crystals appear to be within 1.0 Khz of their spec.

This particular R390 appears to be a low mileage Collins original, still has its original green gear!. It had a short on the audio pre-amp plate circuit. To get it going, I swapped the audio module and the set started working. Needed a ballast tube (I'll replace with 12BA6's for PTO/BFO and short the ballast tube socket) and had 3 weak tubes also. Has anyone tried keeping the 6BA6 PTO/BFO tubes intact and used a diode to replace the ballast tube ?

The PTO has a total 12 Khz error end to end. I know that the ferrite changes over time and thus the error, but is this amount typical ?

Also, I can't get the calibrator adjusted to get to zero beat on WWV. Its close (within 0.5 Khz at 15 Mhz) but the adjustment runs out of range. The oven for the 1.0 Mhz calibrator crystal doesn't feel anything like 75C when I touch its case. Is it possible the oven isn't working and causing the crystal to run low ? Also, the calibrator signal is light at the low freq. end and gets stronger from about 5 Mhz on up. Is this normal ?

Best 73's

Paul - WB2NMI

----- Forwarded Message -----
From: Paul Dulaff <pdulaff at embarqmail.com>
To: r-390 at mailman.qth.net
Sent: Tue, 17 May 2011 02:03:01 -0400 (EDT)
Subject: [R-390] RF Module Adjustable Slug Seperated from Adjusting Screw

I have an R390 which I got working over the weekend. On the 16-32 Mhz slug rack, the front most slug has mechanically seperated from the adjuster screw. I took the slug and adjuster screw out of the set. It appears that the small spring shaft between the slug and the adjuster screw was soldered to the inside of the adjuster screw. Do I just push the small spring shaft into the bored hole in the adjuster screw as far as it will go and solder then back together ? Is there a dimension I need to control to as far as placement of the small shaft spring in the adjuster screw ?

Regards

Paul - WB2NMI
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