[Drake] Drake R4C - Unstable VFO

[Robert Wood]

Hello Ed,

You are correct, I did spray all of the switches with deoxit the first time
around, but I must have not used enough on that crystal switch.  In any case, it
still appears stable this morning, so I plan to put it back into production
today.  I love this radio and it is the one like to operate the most.  Again,
thank you very much for everybody's help.

Thanks,

Bob
K5MBA

-----Original Message-----
From: Ed - K9EW [mailto:k9ew57 at gmail.com]
Sent: Friday, January 07, 2011 9:13 AM
To: radiorob at swbell.net
Cc: drake at mailman.qth.net
Subject: Re: [Drake] Drake R4C - Unstable VFO

Hi Bob,

I think you've found the culprit!

Had the same problem with my R4C, and it would even stop putting out
power (or drop to very low power).  And the problem was the Crystal
Switch.  A little DeOxit took care of it.

I didn't mention this earlier because your first post indicated you
had cleaned all the switch contacts, so I thought there must be some
other problem at work.

The R4C is a great receiver, even compared with today's rigs.

73,
ed - k9ew
www.k9ew.us


On Thu, Jan 6, 2011 at 8:45 PM, Robert Wood <radiorob at swbell.net> wrote:
> Hello all,
>
> I believe I solved the issue and wanted to thank everyone for their expertise
> and help.
>
> I finally got a chance last night to work on the R4C, because the XYL kept me
> busy putting up Xmas decorations over the last few days.  My plan was to swap
> the PTOs between the T4XC and R4C and determine if the problem followed the
PTO.
> As I mentioned in my initial email, when selecting the T4XC as the primary PTO
> the stability problems (CW warble) did not occur.  I took the cover off the
> T4XC, I noticed "T4XC" stamped on the PTO so I decided to compare schematics.
> Well, the two PTO designs are close, but they are not the same HI.
>
> I then decided to turn on the radio and poke around the chassis and components
> with a plastic screwdriver (I learned this trick from my High School Consumer
> Electronics Teacher, HI).  While listening to a CW signal, I poked here and
> there and when I got to the Crystal Switch behind the five crystals I was able
> to influence warbling.  I then sprayed the switch with Deoxit while turning
the
> switch back and forth and the CW signals stabilized.
>
> I have been listening to the radio for several hours this evening and all
> appears well.  I guess age finally caught up with the radio (keep in mind I
> bought the Twins new back in 1975).  I plan to monitor R4C over the next few
> more days before putting it back into production.
>
> Again I want to thank everyone for all of their help and input, I really
> appreciated it.
>
> Thanks,
>
> Bob
> K5MBA
>
> Robert Wood wrote:
>> Hello Drake Techies,
>>
>> I have a possible PTO issue with my R4C.  When listening to CW on any band,
> the
>> signal is not stable (tone jumps around) intermittently.  I do not encounter
> the
>> issue when switching to my TX4C PTO.  When using the T4XC PTO I can work
other
>> stations with no problems :).
>>
>> At this juncture, here are the steps I have taken within the R4C:
>>
>> 1. Cleaned all of the vacuum tube sockets and pins (deoxit)
>> 2. Cleaned all of the switch contacts (deoxit)
>> 3. Swapped 6HS6s (Premix Tube with the 1st Mix tube) no change
>> 4. Replaced the two electrolytic capacitors (C163, and C163)in the 150V power
>> supply section. (I thought I noticed the voltage fluctuating so went ahead
and
>> upgraded the caps)
>> 5.  Tightened the VXO mounting screws.
>>
>> I am thinking about swapping the PTOs between the units to see what happens,
> but
>> before I do I wanted to get other suggestions?  I really appreciate any help.
>>
>> Thank you very much,
>>
>> Bob
>> K5MBA
>>
>>
>>
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