Just got a RAK-8 with power supply and control box yesterday. Dirty but unmolested and in nice shape. I brought it up on the variac, and it works great. I picked up a few NDBs some RTTY and heard WD2XSH/31. After a while I heard a boiling sound coming from the power supply. I found it was coming from the line filter box labeled L-203 in this schematic: http://www.navy-radio.com/rcvrs/ww2/ral/ral-ps-01.JPG I'm guessing the capacitors in there are getting hot. Has anyone opened one of these before? I guess I could bypass the whole thing as it looks like I might end up destroying the box to get it open.

Chris,

I am sure you can safely bypass it but if mine ever fails I will gain entry and replace the failed components.

If you haven't done so, switch the current regulator to the "out" position since you don't need it for fixed station use and it will save 140 watts and a lot of heat generation. I am not a fan of the "output limiter" tube which should be called the distortion generator tube, it can be removed as a spare for use in one of the other positions unless you enjoy significant clipping distortion.

I have a RAK/RAL pair and they are very impressive regen sets albeit quite heavy. I acquired my RAK several years ago still sealed in its foil packet and it intrigued me enough that I begin to search for its MF/HF counterpart. Sometime I will have to compare to see how the RAK compares to my Drake MSR-2 on VLF. The RAL is a very enjoyable CW receiver.

Rodger WQ9E

Hi Rodger,

I haven't removed the box yet, but it looks like the lid may be spot welded on. I'll try some gentle prying. Maybe the spot welds will pop loose. I would like to leave it in the circuit if I can.

And yep, it didn't take me long to turn off that current regulator. I might turn it back on next winter. It would make a nice foot warmer.

I'll be keeping my eyes open now for a RAL. It would be nice to have one to join up with the RAK and control box.

The limiter works well if operated as designed, it cant be overdriven and you will likely find several caps that dont pass a real leakage test. Its about the best storm static reducer Ive ever used for CW.

Carl

I was able to get the can open today and get to the capacitors. I found the lid was held on by eyelets through the mounting holes. The box was filled with tar, so first I tried heating it with a heat gun to pull out the insides in one piece. I couldn't keep it hot enough with the heat gun. An oven may have worked, but I ended up digging out the tar.



Some new caps were installed and its back together and working now.

Yes, I found the limiter worked well to quiet static and electric fence pops.

A week after getting this RAK-8, someone told my dad about an old ship radio they had. I gave them a call and it was a RAL-8! I picked it up today. It's funny how things happen. I didn't think one would turn up nearby so soon.

Chris,

Nice find! It took me several years to locate a RAL to go with my RAK.

Rodger WQ9E

Thanks Roger. Now if only the same thing would happen so I could complete my TCS.

I powered it up Sunday night, and it did work but sensitivity was low and bands 1 and 2 are dead. I found there was 140v on the grid of the 2nd RF tube. The mica coupling cap measured 2.5k on the ohmmeter. A new capacitor brought it back it life.

I have a suspicion bands 1 and 2 are dead because of a problem in the bandswitch.

How were the RAK/RAL muted? I thought I had read something about muting, but now I can't find it. Maybe I dreamed it up.

I seem to recall reading something about a muting box from the TBL transmit/audio control that was used with the RAK/RAL.

BR,

Terry

Yes, something about a muting box is what I remember reading about, but I sure can't find it now.



The problem with band 1 and 2 turned out to be an open antenna coil.

Looks like either lighting or trying to transmit into the receiver took out that coil.

Regens can be a little difficult to mute, unlike a superhet you can't use the AGC to bias the RF and IF sections into cutoff. Killing B+ during transmission will cause a lot of drift upon return to receive.

A simple method is to install a low enough value resistor across the audio transformer secondary (to protect the audio transformer) and then use an auxiliary set of contacts on the T/R relay to open the speaker/headphone lead during transmission. If you wish another contact could be used to short the antenna input to ground during transmission. A little more invasive method would be to install a large value cathode resistor in series with the existing one in an audio stage and use a NC set of contacts on the relay to short this added resistor during receive. Just biasing the RF stages to cutoff during transmission likely would not be sufficient to reasonably quiet the RAL during transmission.

By the way, for those who have a RAK but not a RAL you can use a HF converter ahead of the RAK to turn it into a very effective and stable CW receiver covering the popular ham bands. If you want to cover 15 and 10 this way keep in mind that your converter will need some decent RF selectivity to keep images under control because you are creating the equivalent of a single conversion superhet with a fairly low IF.

Rodger WQ9E

My first was a RAL-7 and PS for $25 at Nearfest about 4 years ago and a RAK-7 was a freebie from a friend a year later.

I used them a bit in the Navy in the 60's as one ship had them in Emergency Radio as backups for the RBB/RBC and TDE also in that room. A TCS-13 on batteries completed the complement.

The RAK/RAL are the ultimate in a factory built regen design.

Carl

Thanks Rodger, and Carl these receivers definitely blow away any other regen I've used.

I noticed that when using the control unit with these receivers, the receiver not being monitored has nothing connected across the output transformer. Was it not that big of a concern because the output is relatively low power?

Luckily that was the only break in the coil and repairing the break got it working again. Whatever zapped the coil melted the wax off the windings, and it pooled inside the can.

I Buili an equivalent RSL-8 with a hybrid cascode bipolar/fet configuration and it has ALL the operating
anomilies of its vacuun tube counterpart. There are two benefeits of this configuration. Increased stability and Incredible sensistivity as well. No tube noise and the first stage is a 1:10 toroid booster xformer feeding an FET stage. this gives at least 20 DB gain ahead of the super quiet Hybrid cascode
current fed configuration of this confiruration. This feeds a 741 op.anp running max gain into a small power amplifier output stage. the performance is quite remarkable as I was able to work HI. from New York under favorable conditions in 1991 with the original RAL-8. The solid state version is much more stable and sensitive, meybe by a factor of 10 of so.

I forgot, I don't think you have to worry about running the audio output X-former un loaded as the clipper circuit will tend to limit any small spikes and the output x-former is rated to take that type of operation with the clipper stage switched off as well.

I forgot, I don't think you have to worry about running the audio output X-former un loaded as the clipper circuit will tend to limit any small spikes and the output x-former is rated to take that type of operation with the clipper stage switched off as well.

You can use photo cell (resistive) control ecross the detector and rf for agc and blanking. I was able to stabilize a lafayette explorair rx with a double photo electric loop control net work to keep the detector running at its maximem sensistivity and could cause it to lock into the incoming signal. If the RAL-8 type of cullent feed back a far greater stagility can be achieved. However the photo electric stabilizing loop control and aditonal stages enabeled remarkable performance.Razor sharp selectivity. Pu the RAL-8 inside of a double loop and watch the stability and performance increase by magnitudes as the Lafayette exploraire did. Remember the double photo electric loop keeps the detector balanced off for maximum selectivity aned sensistivity!