[R-390] IF Transformer Question and New Intro

Tue Apr 9 18:09:35 EDT 2019

Thanks Dave!  I have some used IF transformers on order from Fair Radio to steal the slugs out of.  I may use your WD40 trick to make sure the new slugs can come out.

I just finished the RF and variable IF stage alignment in the meantime.  I picked up a huge amount of sensitivity on most bands!  I kept having to back the SG down to keep the diode load voltage from pegging my Simpson 260.  I started at -60 dBm and ended at -95 dbm for around -7V.  Not that I will ever get to use the new found sensitivity with my ever present S6 HF noise level...

-----Original Message-----
From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> On Behalf Of dog
Sent: Tuesday, April 9, 2019 5:09 PM
To: r-390 at mailman.qth.net
Subject: Re: [R-390] IF Transformer Question and New Intro

I wouldn't say that tool that adjusts the slugs, top and bottom, both, is a special tool. It was in every TV tech's tool box in the 60's. All it consists of is a plastic hex end on a narrower shaft, so you can reach through the top one to get to the bottom slug. I used WD40 on my slugs before turning them. Use the red hose to get the stuff in the bottom slug too. It will evaporate. Just be very careful at first and make sure you don't over torque the slugs, they will break. There was also a recent fix if you can't peak the slugs. Sometimes the 200pf mica cap in the transformers goes south. I had one and they're a bugger to find.

Dave N3DT

On 4/8/2019 21:27, jgedde at optonline.net wrote:
> I remember when I was a schoolkid back in the early 80’s and the 
> R390-a started showing up in the Fair Radio Sales catalog.  I drooled 
> over them!  Then I got various Realistic DX-nnn receivers over the 
> years before getting a Drake R8B and an Icom R-75.  I lost interest in 
> getting an R-390a all these years until I saw the one I bought.  It 
> had to be mine!  All I can say is wow!!!  So it has no sync detector 
> but, so what?  It sounds incredible…
>
>   
>
> From: Larry H <larry41gm at gmail.com>
> Sent: Monday, April 8, 2019 9:09 PM
> To: jgedde at optonline.net
> Cc: Larry J. Haney <larry41gm at gmail.com>; R-390 Forum 
> <r-390 at mailman.qth.net>
> Subject: Re: [R-390] IF Transformer Question and New Intro
>
>   
>
> John, welcome to the group.  These are a marvel, aren't they.
>
>   
>
> All 3 of the 'IF's have 2 slugs (top and bottom) accessed through the one top hole in the IF can.  You need a special tuning tool to access the bottom slug through the top slug.
>
>   
>
> The exception is the Z503 which looks like an IF, but is not.  It's a single tuned coil.
>
>   
>
> Has the killer cap C553 been replaced, yet.  Do not continue to operate until it is.
>
>   
>
> Have fun with your new toy.
>
>   
>
> Regards, Larry
>
>   
>
> On Mon, Apr 8, 2019 at 5:53 PM <jgedde at optonline.net <mailto:jgedde at optonline.net> > wrote:
>
> Hiya Fellas,
>
>
>
> My name is John and I'm not only a new R-390a owner but a new member 
> of the group.  I found a R-390a for sale online and I got good vibes and bought it.
> It cost a small fortune to have it shipped to me, but I scored a 
> working R-390a and I'm having a ball with it.
>
>
>
> My R-390a is a true mongrel.  Motorola power supply, Teledyne IF 
> Strip, EAC AF section, Collins front panel - all circa 1962/3.  As for 
> the crystal section and the RF deck I'm not that far into it yet to know who made them.
> Nonetheless, this receiver is a solid performer and just get's better 
> as I tweak it all back into health.
>
>
>
> Here's my IF transformer question.  In an attempt to readjust the 455 
> kHz section, I cracked two stuck slugs in the transformers - one is 
> backed out almost all the way.  No worries there as I have some new 
> slugs on order from Fair and can get them out using the old coping saw 
> blade trick.  My question is that the Y2k manual and the TM's list two 
> slugs in each transformer.  It says something about drilling or punching a hole in the cans to access them.
> My cans have an existing hole at the top but from what I can see, 
> there is only one slug in each transformer.  Am I missing something?  
> Since I monkeyed with the slugs, I have lost some performance.
>
>
>
> All in all, the R-390a is a masterpiece and runs circles around my 
> modern Icom and Drake stuff.  The R-390a is amazing at pulling 
> intelligible audio out of the mud.
>
>
>
> John
>
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