[R-390] Too Loud Amelco is Dead: Long Live the Amelco

[Raymond Cote]

Was that MCM?

Sent from my outdated iPhone wireless thingy

> On Jun 26, 2014, at 15:46, "Craig Heaton" <hamfish at efn.org> wrote:
> 
> To All,
> 
> It’s time to report my findings. First a little flash back to refresh
> memories. I believe this R-390/A followed me home sometime in February 2007.
> It went thru the usual recap & etc. After a good alignment or two the loud
> audio from either the line or local gain became obvious. Loud audio is
> better than no audio, thus the issue was pushed down the list of thing to
> do. I’d get to it……….mostly on rainy days in Oregon.
> 
> In the past several years everything has been tried many if not dozens of
> times. Tubes were swapped, old tubes replaced with NOS tubes from the junk
> box, tube voltages measured &  compared with a good (to me) Motorola
> R-390/A, IF decks swapped, AF decks swapped, C603’s swapped, another set of
> caps for C603, different speakers, different matching transformers between
> the receiver & speakers. The wiring harness was checked for shorts, opens,
> and grounds. Every wire between the IF going to the AF deck was checked. All
> the plugs/wiring coming or going to the AF deck was checked. Even back
> shells of the plugs were unfastened to look for issues, nada. At this point
> in time I can proudly say all was tried that I could think of, or read.
> 
> The problem, cause, or whatever was on the panel; front or back of the
> Amelco. Both R104 & R105 were good and within spec of 20%. I had a few more
> in the junk box. So I picked the two with the greatest resistance and tried
> them, nada once more. 
> 
> Art Collins please forgive me, I have sinned. R-390/A lovers, you read it
> here first. Both 2.5K potentiometers for R104 & R105 have been replaced with
> 5K audio taper pots. Life is now good. When the phone rings, just turn down
> the local gain. Did I treat the symptoms or find the cause. Darned if I
> care, it works. At the min setting on local gain, audio from the speaker is
> almost gone. One has to listen closely to hear the little sound coming out.
> At a setting of 1 to 1-1/2 the audio is comfortable. Crank the local gain up
> and that ½ watt of audio power rocks the speaker. 
> 
> 73’s
> WD8KDG
> Craig
> 
> PS: ? By the way, the 5K RV4 pots were found on a new internet surplus
> website. Ten bucks a pop and they have 2.5K audio taper pots for that price!
> 
> 
> 
> 
> 
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