[R-390] R390 progress

[Bob Camp]

Hi

I have never torn into the crystal "box" on a 390 so I am just assuming 
it's set up the same way as the 390A. If so then it's not terribly hard 
to get into. While you have it open I would at least pull each crystal 
out and  re-seat it.

There is a test point that will let you figure out if the oscillator is 
the issue. That should give you a pretty good idea how to track the 
problem down.

I'm still betting on an oscillator problem. You could be correct in 
saying that your bandswitch is out of synchronization.

	Take Care

		Bob Camp
		KB8TQ


On Apr 25, 2005, at 10:50 PM, Dan Merz wrote:

> Bob/others,  I pulled the crystal oscillator chassis out of the 390 
> (non-a)
> and got it open down to the heater surrounding the crystals and then
> reconsidered.  I started thinking maybe it's the position of the 
> switch like
> someone mentioned relative to the 390a - I decided to check that before
> tearing into the heater.  I put it all back together and now found 7 
> to 8
> Mhz worked most of the time - good enough to hear at least one ham 
> mid-day.
> But I then checked all the bands using the crystal calib and found all 
> bands
> worked but noticed 4-5, 5-6, 6-7, 7-8 and 8-9 Mhz were quite a bit 
> weaker
> receiving the marker compared to the other bands.  I would say 7-8 is 
> not
> working very well but seems to mostly work.  Occasionally it seems to 
> not
> work.  I tweaked the appropriate  caps and tuning rods a bit at 4.6 
> and 7.8
> Mhz but this didn't seem to strengthen reception much.  I'm wondering 
> what
> to try next to find the problem.  The high bands seem to work ok 
> judging by
> being able to peak the background noise and picking up signals on the 
> ones
> where there's some activity.  That's as far as I got.  Is tearing into 
> the
> heater box surrounding the crystals straightforward ? - the manual I 
> have
> doesn't show that detail or the position of various crystals within 
> the box.
> I guess I should check the condition of the oscillator tubes,  duh !!
>
> I got the line meter to work by putting the missing jumper back on the 
> 11/12
> positions on the rear - seems to be ok now.  The dial calibration was
> correctable from the front panel,  or very nearly so. I'll deal with 
> that
> later.
>
> I appreciate all the help and advice,  Dan.
>
>
>
> -----Original Message-----
> From: Bob Camp [mailto:ham at cq.nu]
> Sent: Monday, April 25, 2005 4:23 AM
> To: Dan Merz
> Cc: r-390 at mailman.qth.net
> Subject: Re: [R-390] R390 progress
>
> Hi
>
> Sounds very good so far!
>
> I would definitely check the crystals for the dead bands. They may 
> simply
> have come loose in their sockets.
>
> The easiest fix of all is the 10KHz offset on the readout. Just center 
> up
> the zero adjust, slip the counter and you're done.
>
> 	Take Care
>
> 		Bob Camp
> 		KB8TQ
>
>
> On Apr 25, 2005, at 2:54 AM, Dan Merz wrote:
>
>> Hi,  I listened to the R390 tonight for the first time after repairing
>> -
>> more to go.
>> So far:
>> Put 12BW4's in place of 26z5's that were missing and rewired the
>> sockets Added two 75 ohm-10 watt resistors below the rectifier sockets
>> in place of missing 47 ohm resistors - a trial to start with,  seems
>> ok Jumpered pins 4/5 to 2/7 and used 12BH7 in place of missing 3tf7
>> Straightened a badly bent twinax female antenna socket Wired a
>> replacement power connector obtained from Fair Added a missing knob,
>> also from Fair Cleaned gear train in place with mystery oil
>>
>>
>> The radio worked once I realized the previous owner had used enameled
>> magnet wire on some added wiring on the rectifier sockets - my
>> connection to it looked good but only connected after I did some
>> scraping to get rid of that enamel !!
>>
>> It appears to be reasonably aligned and  reads about 10 khz high on
>> both ends of the 1000 khz range.  So far only one dead band found up
>> to 20 Mhz
>> which was as high as I checked.   7 to 8 Mhz is dead.  I haven't
>> cleaned any
>> switches so hopefully that's the problem but only one other band
>> showed any sign of intermittent connection.  The line meter appears
>> dead.  The carrier level meter appears ok.
>>
>> I still need a male twinax connector for the antenna socket - one
>> listener indicated he had one but I'm having trouble getting more info
>> from him to pay him so he can send it.  One other response offered an
>> IBM server cable with two connectors that were said to fit,  so that's
>> my backup source at this time.  My local electronics junk collector
>> couldn't help me on this one.
>>
>> Roy Morgan indicated he would provide a drawing/description of the fan
>> he installed on his R390 to cool the 6082 tubes.
>>
>> I was relieved that the radio worked and pleased that it's working so
>> well at this point.  The seller said it played weakly - at this point
>> it is better than that in my opinion and I haven't messed with the
>> tuned circuits at all or changed any of the tubes.  I suspect that the
>> haywired resistors that were stuck in the 3tf7 socket were part of the
>> problem before.  I removed the i.f. chassis to jumper the ballast tube
>> pins and was pleased at how nice it looked underneath there.
>>
>> Now I have to study the manual a bit to see how the alignment goes on
>> the 390 vs. the 390a - more similar than different I suspect,  Dan.
>>
>>
>>
>>
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