[Hammarlund] Favorite Hammarlund Radio

[Carl]

Pat, the NC-183D requires a complete recap of all the paper caps (inside 
plastic covers mostly) and electrolytics as well as 12 or more out of 
tolerance resistors replaced before it will play well. The power and audio 
transformers are prone to meltdown otherwise. Completely done it has well 
under 1uV AM sensitivity for a 10dB SNR.

The 6GM6 is one of the highest remote cutoff pentodes and with high overload 
resistance. On radios with 2 RF stages only the first should be changed. 
Follow the spec sheet for what needs to be changed to run it in spec.
http://scottbecker.net/tube/sheets/135/6/6GM6.pdf
This is usually just a screen and sometimes a cathode resistor....depends on 
the brand and model. If it oscillates the cure is simple, just get back to 
me.

The 6BY6 can be used in any radio that does not use AGC on the existing 
6BE6. It has higher conversion gain and is highly resistant to overload and 
is a direct swap.

Naturally any stage getting a different tube should have the alignment 
touched up.

Ive been touting theses swaps to the SP-600 on another forum and all reports 
have been highly satisfied.

Any radio with a 6BE6 without AGC and a less than stellar RF stage can 
benefit. I even did it to my HRO-60 since I wanted top 10M AM performance 
and National was still back in 1950 as far as tube improvements.

Carl
KM1H



----- Original Message ----- 
From: "Patrick" <wa4tuk-rf at comcast.net>
To: "Carl" <km1h at jeremy.mv.com>
Cc: "Hammarlund Radios" <hammarlund at mailman.qth.net>
Sent: Sunday, December 11, 2011 10:30 AM
Subject: Re: [Hammarlund] Favorite Hammarlund Radio


> Carl:
>
> I've got a NC-183D that I'm already pretty well pleased with. Right now 
> it's used a a band cruiser for AM broadcast, some shortwave and ham AM up 
> to maybe 15 mHz or so. For SSB I'd just choose a more appropriate radio 
> although it should be fine for CW.
>
> I've  got enough gain to bring the local noise level up to S7 or more 
> below 15 MHz but I can't say the upper bands are too sensitive.  What sort 
> of improvement did you see with the 6GM6 and 6BY6?  Looks like they have 
> the same base as the originals.
>
> Also, would you guess that this sub would be appropriate for the HQ-145 or 
> 170?
>
> Pat
> wa4tuk
>
>
>
> On 12/11/2011 8:21 AM, Carl wrote:
>> I had one also in the 80's and was unimpressed with its performance even
>> after a full overhaul. Drift was present but the front end noise was the
>> killer. Considering the tube lineup a NC-183D was better.
>> After rebuilding a few others I started using the 6GM6 first RF and 6BY6
>> mixers and the improvement was very noticable. Some customers still want
>> them left completely original.
>>
>> Carl
>>
>>
>
>
>
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