{Collins} R388 Progress

Hello all.

Been awhile since I've posted on my R388 progress. I was distracted by a Viking Valiant restoration. 

I've nearly completed my restoration and I've run into some common issues with the crystal oscillator. Note the following:

1. I've read in other posts that one should turn off the AVC and reduce RF gain to minimum while performing the crystal oscillator alignments. The manual does not mention this step. Which is correct?

2. I am using 2 - 1Mohm resistors in parallel to get 500K; within 10% of 470K for the RF probe to pin 7 of V102. Is this okay?

3. My instrument is a HP Counter / DVM, model HP5326. The specs list a 1 Mohm input Z for the DVM portion.

Alignments seem dead on for most of the bands. However, the alignment on the 20m is very far out near the edges; so much so that fiducial tweaking is not effective.
The VFO/PTO linearity is not bad on the 2-3 MHz band. Its variation is less than 5 KC on each end, so I guess I got lucky on this one.

I've adjusted all the caps per the manual for 2V; although when I am reading on the DVM, its actually -2V.

I suspect that one or more of the crystals is way out of spec.

What is the consensus?

I'll forward more info tonight if needed with actual deviations per band.


Philip KA4KOE

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