[Milsurplus] FRR-59 Adventures

[John Vendely]

That blocking oscillator transformer seems to be a high-failure item in 
the FRR-59 and WRR-2.  I have three FRR-59s, and had a coupla WRR-2s 
decades ago, and of these five receivers, three experienced blocking 
oscillator transformer failures, two upon receipt, and one of them a few 
weeks after finishing the receiver overhaul.  I fabbed some replacement 
transformers with good results, and they're still in service. Symptoms 
and component fault was similar to what you describe.

Enjoy working on yer receiver, they're unique, and a lotta fun...

73,

John K9WT

On 9/29/2017 12:03 PM, Bruce Gentry wrote:
>
>    I found an FRR-59 about a month ago and began restoration. Thanks 
> to parts from others on this group, the lower sideband decoder is now 
> working and the 100 KC digit counter is replaced. I made careful notes 
> of the positions of everything with the old counter turned all the way 
> counterclockwise, set the replacement the same way and installed it.   
> Powered it up, and thought everything was going great. The continuous 
> tuning calibration was surprisingly close.  Next, I tried the 500 
> cycle incremental tuning. It worked...for about 10 minutes and quit. 
> It was too late to continue so I left it for this morning. I turned it 
> on, and the incremental tuning worked great. I quickly switched it 
> off, got a note pad and my scope ready, then turned it on and sampled 
> the waveforms  in the blocking oscillator stage. As I had expected 
> would happen, it quit working- and the waveforms coming out of the 
> blocking oscillator were totally whacko. Then I noticed the B+ on the 
> stage was jumping by about 20 volts. A check showed the entire 160 
> volt buss was going bonkers. That turned out to be the filter 
> condensor sockets were loose. The negative terminals of the condensors 
> were connected to the shield rings on the sockets. With the anodized 
> aluminum chassis and loose screws, the condensors had a very poor 
> ground. I wired the negative pins of the sockets directly  to the 
> negative side of the rectifier, remounted the sockets tightly, and the 
> B+ jitters are gone. Then, of course, the incremental tuning quit 
> working. The waveform coming out of the blocking oscillator was pure 
> hash. The primary of the transformer was reading about 200K ohms and 
> going all over the place. For grins and giggles, I found a couple 
> small cup cores and made a transformer. It works great!  I  left the 
> receiver on to cook all night  and it is still working fine this 
> morning, the incremental tuning is still fine.   If it is still 
> working after a few days, I will tackle the alignment of the front 
> end. The lowest band is off by 100KC so the harmonic amplifier is 
> misaligned. Even so, the sensitivety and selectivety are great. I am 
> going to make a guess the epoxy encapsulation on the pulse transformer 
> corroded the winding or tore a connection loose.  I  may drop it into 
> a jar of acetone and see if the encapsualation dissolves, see how it 
> failed, and see how far off from the original my homebrew transformer 
> is. I am still looking for the connection "blister" panel for the back 
> of the converter section cabinet and the studs or buttons that secure 
> it. It would be nice to be able to put it in the cabinet rather than 
> having the wiring jury rigged on the bench.   The saga continues, and 
> is a good warmup for a Russian R-155 that is on it's way to me :)
>
>      Keep the soldering irons hot and the suds cold!
>
>       Bruce Gentry KA2IVY
>
>
>
>
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