[R-390] FW: Thursday's Line & Local report

[Craig Heaton]

Hello Bill,

Shortly there might be more hair on my arms than on my head! As to tubes:
The correct tubes are in the correct sockets, checked all with a TV7DU,
moved them around watching for a change, nada. 

Friday's Line & Local Report

Made a trip early this morning to the shack and made progress, but no cigar.
All the battle weapons are scattered in the shack and are being used. With
that, on TB601 the resistor R608 was touching a jumper. Under TB601 the
solder area of R608 had a slight contact with the jumper from Pin #5 of V605
that goes to E607. That jumper was of a generous length and had quite a
curvature up towards the TB. Don't remember last time I've checked E607, but
sometime in the past I'll guess the voltage was checked. 

Now the voltages on terminal #1 of the Line & Local pots agree with the
normal Motorola. The audio hasn't changed. A little dissertation is in
order. 

1. I have bad hearing, or so the audiologist said. 
2. With the door of the shack open, I can follow QSO's outside in the
backyard 20 feet away.
3. With the door of the shack closed, the voices are audible but not
understandable.
4. This is with the Local gain at zero.

Considering the solder job of the 5K Local pot that came with this R390/A
was first class, it is time to knuckle down and trace every wire &
component. I might be dealing with someone's better idea.

I will beat this receiver into submission!

Regards,
Craig
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-----Original Message-----
From: Bill Cotter [mailto:n4lg at qx.net]
Sent: Friday, January 03, 2014 7:40 AM
To: Craig Heaton
Subject: Re: [R-390] Thursday's Line & Local report

Hi Craig,

I'm sorry to see you tearing out your hair on this AF too-high problem. A
customer brought me a Collins 51S-1 complaining of low audio, opposite of
your issue. First thing I did was to check the tubes to get that out of the
way before digging in. Low and behold, someone swapped a 12AU7 dual-triode
for the 12AX7 in the audio chain. The audio came up 20-25dB at the AF Gain
full-on position. 
Easy fix.

Where I am going with this is have you checked all the tubes in the AF chain
and made sure that the 12AU7's are really such? A wild card, but you never
know.

73 Bill N4LG




At 08:38 PM 1/2/2014, you wrote:
>Good Evening All,
>
>The house work is complete till next time. A strange bright globe in 
>the sky made an appearance here in the PNW. After the chores were done, 
>it was time for a walk and soak up a mega dose of Vitamin D. More rain 
>and fog in the forecast.
>
>The Amelco: About a half hour or so was spent measuring P120. In brief; 
>no grounds, shorts, opens, & all wires were to spec. Pulled, twisted, 
>yanked, and tortured P120 and couldn't find any faults. Next up was
>C603 and the TO-6A. All three sections measured around 30uF. 
>Considering the dial and the age of the instrument, I'll call that 
>good. Then all three sections were tested for leakage at rated voltage.
>At 300 volts, all three measured under 0.01mA of leakage. I could dig 
>up the receipt for the replacement caps in C603, the voltage rating 
>might be higher but what the heck.
>
>Tomorrow I want to look at the AGC line on the Motorola. O'beer 
>thirty........
>
>Regards,
>Craig
>
>
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