Collins 32V-1 and 75A-3

 32V-1 Transmitter

September 5, 2025 - Additional testing and after using Deoxit on the band switching, now all bands are functioning.  The remaining item to get working is the microphone - I know the element is working as I looked at it on my oscilloscope while speaking into it - the wiring inside the D-104 base looks correct - next is to check the plugs wiring.

 

August 31, 2025 - Replaced the 100 ohm plate suppresser and installed a new ceramic plate connector - still same issue with the grid and plate meters.  I decided to go back to the original tube and the issue went away - this tube does not have the "blue" emission in the top like the other (bad) tube - I guess the bad tube is gassy.  Seeing 90W with HV on 600V on one of the bands - will look at tuning the other bands.

August 25, 2025 - This issue has been  resolved.  I did not realize the cause until I looked at the schematic, but every time I put the transmitter into voice it would key continuously, so what I found was the PTT line is tied to the high voltage switch so turning off the high voltage switch, and then using the PTT on the microphone to key the transmitter resolved that issue.

A new issue - After replacing a few tubes, I'm now getting good power out but seeing negative meter movement on the grid current and sometimes the plate current meter pegs and the only way to fix that is power cycle the HV - my plan is to look at the components around the output tube and start checking those. Maybe some of the capacitors are leaky or have gone open or closed. 

August 23, 2025 - The relay has been cleaned and is back in place.  I installed a new SO-239 connector and still need to replace the power cord.  With 700V I was seeing over 100W and with 600V I get 53W on the band tested.  Also the new dial needs to be installed.

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

7 September 2025 - Finally got thr Collins speaker that I bought a a Dalton hamfest several years back.

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.

June 14, 2025 - Picked up the equipment.  I got seven tuning units for the BC-375.

 TU-5B        1500-3000kc            (two)
 TU-8B         6200-7700kc            (one)
        TU-10B        10000-12500kc       (three)    
TU-26B        200-500kc            (one)

Here are some pictures of the inside.

June 10, 2025 - Will be picking this all up on Saturday.

June 4, 2025 - Just bought all this for $250 - The BC-375 is a little rough but complete per the seller.