After the epoxy cured, I painted the world of the restore with silver paint to match the color of the aluminum. I applied a small quantity of epoxy to fill the crack that had been the outlet. However, outdated residue is usually degraded and present in a lot smaller quantities than recent materials, so the quantity transferred could also be restricted. Out of curiosity, I changed the two 6SG7 tubes with NOS examined-good 6SK7. There wasn’t an excessive amount of distinction in reception except the AVC now appeared to work significantly better (remember, R27 continues to be one hundred ohms.) I used WWV 15mc for a excessive frequency sturdy signal and 4mc with an HP606B strong signal supply for a low frequency. When using the RAO-7, it turns into obvious that the AVC has method too much unfavourable bias and when the receiver is operated above 10mc within the AM mode, the AVC responds to the received noise quite than the tuned signal with the AVC slicing back the sensitivity. I used to be surprised on the stability on 20M and especially involving a SSB signal.
Possibly among the AVC resistors may have drifted in worth permitting simply sufficient AVC bias to be out there for 20M signal power however not sufficient adverse bias to regulate 75M signal strength. After allowing this to harden , the finish was rubbed down with 0000 steel wool to dull the shine a bit. A combination of equal components of lacquer thinner, denatured alcohol, and acetone was used to reflow the finish in locations the place it had develop into worn. This was allowed to dry for a few days, then a number of coats of Clear Gloss Nitrocellulose lacquer have been utilized. This exhibits the cabinet after the coats of toning lacquer have been utilized. After putting SN:394 on the bench and eradicating the bottom covers, it was unfortunately very obvious that nothing could possibly be decided from SN:394 as a result of virtually every resistor on the 2 IF tag boards, along with most of the resistors in the receiver, have been replaced. Other Questions – Though R27 in SN:665 seemed like the original resistor, there was loads of “non-authentic” soldering on the terminals and the cloth-insulated wire lead situation and resistor lead wraps didn’t look original. New reproduction knobs have been installed as the unique ones were badly warped and not usable.
Sweeter flavours similar to our dessert vary can fall sufferer to this, although as we’re conscious of this, we work to ensure they don’t seem to be as liable to it. But, the straightforward solution is the just turn off the furnace – problem solved. Now, the receiver sensitivity is barely improved (noticeable however not over-whelming) But, the numerous enchancment is now the Matchbox does “peak” the receiver response which signifies that the antenna Z and the receiver enter Z are a fairly close match. When adjusting the RF achieve, with the AVC on, at above 15 there isn’t anymore increase in sensitivity for the reason that AVC has management at that degree on sturdy alerts. An alignment peaked up the sensitivity of the set fairly a bit. Was a subsequent alignment of the IF section a part of the improve? An alignment of the IF additionally might show helpful to stability and performance. I put in a 270 ohm resistor as a take a look at and that worth seems to work fantastic with 6SK7 tubes (I’m contemplating altering this 270 ohm value to around 400-500 ohms for better IF achieve stability using 6SG7 tubes.
This greater worth tends to maintain the IF stage acquire cheap and stable. It seems logical that the CSR-5A adjustments were to profit the receiver’s efficiency in that major mode of marine communication. I feel it is comparable to the USN RAO-7 receivers that seem to operate fairly nicely on all unique components. However, SN:665 has what appears to be like like the original R27 installed and it’s a one hundred ohm resistor. SN:394 has R27 put in as a fairly new type Allen-Bradley 470 ohm 5% resistor. Finally, after thinking in regards to the a thousand ohms in sequence with the antenna input, it became mentally obvious that the input Z is a minimal of 1000Z as a result of series resistor. The primary windings needed to be connected in parallel for 117vac operation and the 2 secondary windings had to be related in collection for 12.6vac. I used an AC “zip cord” with molded plug for the first connection to the house AC line (with “bucking transformer” to lower the AC line from 122vac to 116vac.) I used take a look at clip-leads for the secondary connections to the receiver. I didn’t want to unsolder the IF transformer, so I eliminated the three, facet-mounting screws that hold the IF transformer meeting inside the shield-can.
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