[Hammarlund] Favorite Hammarlund Radio

[Patrick]

Carl:

When I got the receiver it would barely make a sound.

I replaced all of the paper caps, most of the resistors, and one 6sn7. 
The electrolytics were recent manufacture and not too badly done by a 
previous owner. I can't know for sure but I think the tubes are all 
original except for the 6sn7 with a dead half. Most were RCA dated 43-56 
that still test and operate well.

I'll certainly agree about the resistors. All of the 47k used mostly for 
screen resistors were extremely high or just plain open.

Thanks for the tube information. I'll give those types a try.

Pat
wa4tuk


On 12/11/2011 6:49 PM, Carl wrote:
> 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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>
>
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