DR-200 - 10.245 L.O.

[kd1nw]

Hi,

I've been trying to get a Monitoradio DR-200 working and the 10.245Mhz osc doesn't oscillate unless I place a clip lead on Pin 2 of V8A (6U8) and leave it floating. I assume this is forming a gimmick and the 10.245 mhz is coupling just because of the proximity of Pin 1 and Pin 2? I am right in thinking C45 (4pF) is bad? I tried a couple of series connected 7pF across C45 but that didn't work.

Thanks 73
Kevin - KD1NW

[KD6VXI]

I'm interested in this answer as well.   Back in my Cb bench tech days,  I had a 30 dollar Kraco set that would work perfectly if I scoped the first if xformer.  If I used a cap to ground to simulate my probe,  nothing.   Remove probe,  nothing.   As soon as I put the probe on the xformer,  set worked perfectly.

I shotgunned every part around,  nothing fixed it.   Ended up scrapping the he unit,  not worth repair.

Sounds very similar.

--Shane
KD6VXI

[W4AMV]

Hi,

C4 controls the injection level of the LO to the mixer. A second order affect, it partly contributes to the termination C of the xtal, which appears to be 32 pF, a standard value for parallel mode crystal operation. If you have another xtal, try it. If not, then replace the xtal with a series L (plus a blocking C) where the L needs to look like 32 pF of inductance at 10.245. That is about 7.5 uH. See if the LO runs ok then.

[N8ETQ]

  Hey Kevin,

       Could just be a bad rock.. You could inject 10.245mc
into pin 9 of the 6u8 and if the thing comes to life and works
solid, then you just have to try another 6U8, the triode
half of 6U8's always give me trouble.. Just ask my CE-100V.

       If it wasn't hooked to a 6U8, I would say it's the rock.

GL

Please keep us posted..

Thanks

/Dan

[WD8BIL]

In desperation I've removed the crystal and re-installed it 180 degrees from original. Works most of the time.

[N8ETQ]

   Almost all of those old crystal synthesized CB sets
had a 10.240mc rock in em... 

/Dan

[N8ETQ]

     Did you try re-heating the slober joints in that area?

/Dan

Hi,

I've been trying to get a Monitoradio DR-200 working and the 10.245Mhz osc doesn't oscillate unless I place a clip lead on Pin 2 of V8A (6U8) and leave it floating.
Thanks 73
Kevin - KD1NW

[Pete, WA2CWA]

Did you try the obvious; adjusting L12?

[kd1nw]

Hi All,

Thanks to everyone for responding. I had tried most of what was suggested, sorry I should have put that in my post. First, I tried multiple 6U8 and 6EA8s. I tried cleaning and reversing the crystal connections. Then, I verified the tube and crystal produced oscillation in a second working dr-200 that I have here. The 6U8 and crystal in the defective radio work fine in the working radio. I then tried adj L12 and no amount of adj worked. Then I noticed it came to life when I was measuring pin2 voltage. So, instead of having the meter attached I tried just the clip lead and it still worked like that.  Adj L12 with the clip lead on I can put it right on 10.245. It receives signals but it's pretty insensitive. I'll try and get it on the bench today and try signal injection and reworking the solder. The radio has been worked on in the past so maybe there is a bad joint there somewhere. I'll also get some caps for the ones in the general area and try replacing them.

Thanks and 73 - Kevin KD1NW

[kd1nw]

Hi All,

I just got the 10.245 LO working. I replaced all the caps, 4pf, 2x 27pf, 100pf and 1000pf and no change. Adjusting the secondary of the transformer where C44 (27pf) is attached did it. The radio receives now but sensitivity is low. I'll bet some of the other transformers before it have been misadjusted. So Shane, your situation and mine were very similar. Maybe the above adjustment would have  worked for you?

Thanks 73 - Kevin KD1NW

[kb2vxa]

You found the problem before I had a chance to reply, in a nut shell somebody put the golden screwdriver to it. That having been said comes the obvious, complete alignment is in order. One of those came to me some years ago, a Hallicrafters CB3A a YL "cleaned". It was dead as a door nail after she cleaned the dust out, that wouldn't kill it so I asked what ELSE did she do with it. "I tightened the loose screws."

"Oh, mama, can this really be the end? To be stuck inside a mobile with a busted mic again."
Bob Dilly