[R-390] R390 (non-a) low audio

[Kevin McGrath]

Thanks, Norman (and all who responded privately). I took your suggestion of comparing to my R390 non-A to my R390A, the A has much better audio levels. Then I noticed a boneheaded hookup error -- I had the speaker and transformer hooked up to the "phones" screw on the terminal block. When I moved it over to the speaker output, the audio level was much better. With local gain set at 5, the non-A now has a comfortable listening level.

I found a set of 7 and 9 pin tube extenders (and extractors) on Ebay, so I'll be able to perform voltage checks as needed on either rig in the future.

Kev





>________________________________
> From: Norman Ryan <nnryann at yahoo.com>
>To: Kevin McGrath <kj_mcgrath at yahoo.com>; "r-390 at mailman.qth.net" <r-390 at mailman.qth.net> 
>Sent: Saturday, July 6, 2013 9:38 PM
>Subject: Re: [R-390] R390 (non-a) low audio
> 
>
>
>Hi, Kevin,
>
>Audio will be slightly weaker with a 1000:8 transformer.  But if your R-390A audio is working OK, listen to it, then hook the transformer up to the R-390 and compare results for a sort of baseline.
>
>A readily obtained 70 volt line audio transformer will work like a 600:8.
>
>It's possible the IF deck gain is merely incorrectly set.
>
>Check tubes on a tube tester or substitute one by one with known good ones.  
>
>Voltage checks are done with the tubes in their sockets, for which socket extenders are used.  Resistances can be measured with the tubes out.  For the latter, turn off and unplug the power; but you know that already, right?
>
>Good luck and let us know how it goes.
>
>73 de Norman, KG4SWM
>
>
>
>
>
>
>
>
>>________________________________
>> From: Kevin McGrath <kj_mcgrath at yahoo.com>
>>To: "r-390 at mailman.qth.net" <r-390 at mailman.qth.net> 
>>Sent: Saturday, July 6, 2013 3:19 PM
>>Subject: [R-390] R390 (non-a) low audio
>> 
>>
>>I have recently acquired an R390
 non-A -- in addition to the R390A I bought last month. (Egads! does this mean I am hooked!?).
>>
>> I have set about getting the R390 working again and have made progress. So far I have replaced the low voltage rectifier (CR108) to get the antenna relay working; fixed a loose connection on the Line Audio switch to get the Line Level meter working and fixed the low B+ voltage (was only 135v) by replacing C608 in the AF unit.
>>
>>At this point it is receiving signals, but the audio level is low even with the Local Gain set at 10. So I am about to do the voltage and resistance checks in the AF deck.
>>
>>I have a R390 newbie question regarding the voltage checks at the tube sockets. Are they done with the associated tubes still in place? If so how does one get at the pins...use a tube extender? Or are they taken with the associated tube removed and probed from the top of the empty socket?
>>
>>
>>I am using a 8 ohm speaker with a 1000:8 ohm
 transformer from radio shack. Sure, it's not the proper 600:8 ohms but I wouldn't think the mismatch would result in low audio levels when running the Local Gain wide open.
>>
>>Any other tips for investigating low audio are appreciated.
>>
>>Kev
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>