KD4APP - Ham Radio: August 2025

Friday, August 22, 2025

Collins 32V-1 and 75A-3

32V-1 Transmitter

August 21, 2025 - Cleaning the relay and checking that it actuates when HV tis turned on. It looks really dirty still - been using lots of contact cleaner but still no RF output.

August 17, 2025 - After replacing the LV 4uf capacitors I was seeing grid and plate current and a small amount of output power. I decided to check the tubes in the exciter and found the 1st multiplier tube was bad and have ordered a new 6AG7. Also found some writing on the bottom of the plate covering the exciter which noted the tubes were changed in 1954 & 1966.

August 16, 2025 - Got the two 4uf capacitors replaced yesterday and seeing frid and plate current again.

August 14, 2025 - Been working on checking the electrolytic capacitors in the 32V-1 - found the HV 8uf is good bit the two LV 4uf capacitors (second picture below) need replacing. Also got a picture of the tag - the serial number is 435.

July6, 2025 - Re-checked the power out and it was 27W.

July 5, 2025 - Yesterday I hooked up a key to see if there was any output. Today I hooked up the Bird watt meter and was seeing around 30w - I will check again once I get the tubes I found faulty in the LV & HV power supplies replaced.

July 3, 2025 - Got the replacement lamps for the LV (green) and HV (red) indications. The lamps are 15 Watt - T4.5 Incandescent Light Bulb Clear - Candelabra Base - 130 Volt - PLT IN-0015T45CL and I ordered them from 1000bulbs.com .

June30, 2025 - Tested the LV, HV and modulator tubes yesterday - found a few that need replacing and ordered some and have bids on others.

June 28, 2025 - Almost two years later this project is finally on my bench. The LV and HV are working, but not sure I am getting the expected voltages. I will be testing tubes and capacitors in the power supply section next.

4 July 2023 - Finally got around to getting the 32V-1 out of the cabinet - first task was to replace the LV & HV lamps - next will be to check the two 4uF capacitors in the LV section.

I have the replacement dial from Howard Mills and I also have velum paper and the lamps for the dial segments.

18 October 2022 - Looking at a few items before firing this up - the 4uF capacitors in the LV section look leaky and they are deformed - ordered replacement capacitors for them and the two in the HV section. I may re-stuff them or may just bypass them under the chassis, installing the new capacitors there.

17 October 2022 - Picked up the Collins 32V-1 receiver on 10/15 - this radio is extremely heavy - looking forward to testing it and getting it operational. I already have the replacement dial rule.

22 September 2022 - Adding a 32V-1 transmitter to my Collins collection - just won the auction at $199.99 - a steal.

75A-3 Receiver

20 November 2021 - So far I replaced the limiter pot - it was frozen. Added another filter in the "B" position.

I ordered and received a complete tube set, capacitor replacement kit, and a SSB adapter. These will be installed at a later date.

Tested on multiple bands and works great - even SSB without the adapter works

BC-375E and BC-342

August 18, 2025 - The serial number of my BC-375 is 65672 - I need to start checking capacitors and see if any of them are shorted out and causing the HV fuse (FU-12-A) to blow.

August 14, 20225 Schematic of MO and PA.

August 2, 2025 - Put some small 12v LED's that come with the wires, in place of the bulbs in the BC-342 - they are a "warm white" and look like the originals.

July 27, 2025 - Here's the fuses in the PE-73 dynamotor.

USE Number SPECS
Filaments FU-13 30A 250V
LV FU-22 60A 250V
HV FU-18-A 1A 1000V

July 24, 2025 - Checking further on the RF output I reviewed the schematic yesterday and decided to check the fuse shown below - it's a FU-12-A and .5A at 1000V - it was blown and the spare in the chassis was also blown, so I ordered four on eBay - I will replace it and see if there is another issue or if that allows RF output. On the 28V side I see 15A in voice mode. Also shown below is the hookup to the RF connectors that is going to my BIRD wattmeter and a dummy load.

July 22, 2025 - With the HV cable and the other power cable for 28v and on/off wiring, I tested with the battery and power supply parallel. Still no RF output power.

July 20, 2025 - Ran the dynamotor on the new power supply. First picture is the CW voltage - it's lower than normal because the Oscillator tube is a HY-69 rather than a 211, and it uses a 6V filament as opposed to a 10v one. The second picture is the two modulator tubes and they are within range at 10v. Next test I will parallel the battery with the power supply - this should smooth out the startup of the dynamotor.

July 15, 2025 - Yesterday I had to use a separate power supply to engage the relay as the power switch was not doing that - after studying the schematic I decided to reseat the tuning unit as I figured either the on/off switch was bad or the "interlock" switch was not functioning - reseating did the trick and the dynamotor now comes on - I saw 11.27A. I've ordered a 28V military power supply - and will parallel it with the 100A battery. Next task is to build the HV cable which will supply the 1100V DC.

July 13, 2025 - Brief test of the PE-73 dynamotor today while I work on assembling the cables. I used a separate power supply to engage the contacter and a 100A LiOn Battery to power the dynamotor. I saw a 6A dram for the dynamotor alone.

July 1, 2025 - UPDATE on BC-342 - All is well - I had plugged the speaker into the headphones jack and that was the issue - using my headphone in the headphone jack and I was able to pickup signals on all bands tonight. The issue I see if that the dial is not aligned with the frequencies - I believe this is just aa simple set screw behind a cover beneath the dial. I will look into this tomorrow,

July 9, 2025 - The BC-342 worked great on the lowest bands but it seems to be more and more deaf in the higher bands. (see update above)

July 8, 2025 - The Dynamotor arrived and I connected the 28V input cable. I also ordered two PL-59 connectors for the HV connection.

July 7, 2025 - Tested the BC-342 downstairs and injected a signal on 1600 KC from my signal generator and the sensitivity was great. This is with the replacement 6C5 tube. I was also able to hear traffic on 80-meters on one of my secondary antennas. The LS-3 speaker for it also arrived and tested good with the BC-342.

July 2, 2025 - Bought a PE-73 dynamotor.

July 1, 2025 - The VT-4/211 tubes arrived and I put them in - looks pretty cool!

June 25, 2025 - First power up with just the VT-25 (speech amp) tube in it. I have the other VT-4 tubes on order. The BC-375E can operate in CW mode with just the Master Oscillator and the PA tube in place.

June 25, 2025 - Ordered the four 211 tubes yesterday from a Chinese supplier on eBay - just under $135 per pair. Also some old pictures of BC-375's in action. Bid on a dynamotor today.

June 23, 2025 - Got the painting completed. The paint on the tube cover is still a little wet, so I expect it to look like the right upper antenna tuner panel when dry.

June 22, 2025 - Today on the BC-375 I masked off and painted the antenna tuning unit top half and a small section on the left half of the main control section above the band tuning unit and a small section of the lower antenna tuning unit. I also painted the sides. I still need to paint the cover over the tubes, the top of the unit and the back.

June 21, 2025 - Checked the tubes in the BC-342 and found one of the 6C5 tubes tested bad so I ordered a replacement. Here's the inside of it.

June 18, 2025 - Here's the BC-342 - it looks great - will be testing it soon.

June 15. 2025 - Here's what the tube complement will look like and their functions. In my unit someone replaced the second from the left tube with a 5-pin socket and a HY-69 tube. I have purchased a 4-pin socket to put it back as a VT-4 tube.