[Hammarlund] Favorite Hammarlund Radio

[Carl]

Subject: Re: [Hammarlund] Favorite Hammarlund Radio


> 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 wouldnt put much faith in a tube tester especially for tubes in RF stages. 
Some NOS ones arent a big expense as they are garden variety 6BA6 and 6BE6.

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

The 183D is notorious for that and the high values in the AVC and audio are 
also suspect.

Retube and do a good alignment and you will be pleasantly surprised. Then do 
the swaps as you want to set a baseline first.

Carl

>
> 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
>>>>
>>>>
>>>
>>>
>>>
>>> -----
>>> No virus found in this message.
>>> Checked by AVG - www.avg.com
>>> Version: 10.0.1415 / Virus Database: 2102/4074 - Release Date: 12/11/11
>>>
>>
>>
>>
>
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 10.0.1415 / Virus Database: 2102/4075 - Release Date: 12/11/11
>