Collins 32V-1 and 75A-3 and 75A-1

75A-1 

April 19, 2026

Update - Purchased this from Brian KN4R before the Dalton Hamfest and received it there - he reported no audio - have have tested most of the tubes and found two tubes that were testing bad and needed to be replaced - I have received them but have not had time to put the in and test.

32V-1 Transmitter

April 19, 2026

Update - this has been on the bench a while - everything is working except voice - this is still on my main bench waiting for time to work on it further.

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

HP-403-B AC Transistorized AC Volt Meter

 

April 11, 2026 - Buttoned it up.

April 9, 2026 - Working!!!  The 1/16A fuse and spare was installed.  Just needs calibration.

April 6, 2026 - Batteries installed and working - meter pulsates on startup so not sure if that's normal as it does settle down - pegs when turned on, then goes to zero, then goes about half way up and then goes to zero and goes up slightly and settles to zero.  Next I need to test measuring some AC from my isolation transformer.  I have the correct 1/16A fuses on the way - using a 1/4A in the meantime.

April 3, 2026 - This arrived a few days ago and started working on it,  First task is to replace the batteries.

BC-610-H and BC-614-E and BC-939-B and JB-70

March 8, 2026 - Completed wiring od JB-70-W except the coax relay.

March 5, 2026 -  More work on the JB-70 substitute.

March 3, 2026 - More work on the JB-70 substitute.

February 25, 2026 0 This arrived - not packed very well but it looks like it survived - the crank handles were bent but I was able to straighten them out.  All the knobs and cranks seem to function.

February 19, 2026 - Purchased a BC-939-B - it's on the way to me.  The lot of coils I purchased also arrive on 2/20 - pictures of them soon.

February 16, 2026 - These arrived - I need to take an inventory nut I believe I should have a full set now.

February 6, 2026 - Started building the cable for my JB-70 substitute.

January 26, 2026 - Got the key working through the BC-614 - the issue was me - I didn't have the BC-614 switches set correctly.  Also got my Bird meter with the 1000W element in-line - saw 360W with unit keyed in high power.  Now all I need to do is try another carbon mike - the one I tried is unknown. Update - same results with another carbon mike.  I'm going to start looking in the BC-614 - lots of old capacitors in there.

January 25, 2026 - Measured the voltage on tbe 100TH socket and saw 5.0 volts.  Decided to spray some Deoxit and move the tube on which the filament was not lighting - that worked and now the filaments in both tubes work.  Now to look at the BC-614 and see why the key doesn't key the BC-610.

January 16, 2026 - The last few days I have been testing on high power and getting 300+ watts and on low power setting I can easily get 100 watts.  I am still trying to find out why only one of my 100TH tubes the filament lights when in either socket.

January 10, 2026 - I have been putting the BC-610 back together and ordered and received a pair of 100TH tubes as one of my originals got broken and the other seemed to be gassy on the bench - I could never get the filaments to light up in the BC-610 and was trying to figure that out.  One of the new tubes I received had a metal base and the filament will light in either socket so I have ordered another one with a metal socket - scratching my head on this.

 

January 1, 2026 - Got the top deck back in place (not shown) and put the cover on top (not shown).  I broke my one good 100TH tube so I have ordered a pair - should arrive the week of January 4th.  Below is some pictures of the middle modulation deck.

December 24, 2025 - Got the top chassis out and replaced the grid resistors - one was broken and the other measured 52 ohms so I believe it was still good but replaced it anyway.  i have left the top chassis just sitting in place - next plan to take out the middle chassis to check it.

 

 December 23, 2025 - Ready to remove the top chassis in the BC-610 to fix the grid resistor that's broken and check on other components in it.  After that I will remove the second deck and see if I can figure out why the 100TH's heaters are not working when in the system - they work if I connect 2.5v to them outside the unit.

November 23, 2025 - This past week I fixed the wires from the carbon mic jack that a previous owner had cut - I also slowly powered up it up (back-hot / red-neutral) on my insolation transformer.

November 15, 2025 - Completed msle plug - updated after I turnrf the shell key about 15 degrees counter-clockwise to line up.

Completed the female end (bottom) of the BC-614 to BC-610 cable and started on the male end (top) yesterday.

 

November 8, 2025 - Working on the BC-614 to BC-610 cable.

November 7, 2025 - Yesterday I fixed the light over the tuning units - after moving it back and forth a few times in its socket, it finally came on with the filament power.  HV power seems fine - still getting 70W with the HV protect switch in the middle.  I have been slowly removing the side panels and have them off now - next on my list is to get the top (exciter) deck out and replace the grid resistor on the 807's where the one on V11 is broken.  Aft4er that I can take the modulator deck out and see why the filaments in the 100TH's are not lighting.

October 24, 2025 - Checked with Mac W4AX to see if he knew what the device was that was hooked to V11 pin 3 (grid 1) - he said that device is used to bypass the oscillator and you could use any radio that could put out about 12W.  Also discovered that R22 that was connected to that pin was broken (or cut).

October 23, 2025 - Making progress - 70W.

October 21, 2025 - I may have resolved the grid issue - removed this contraption connected to pin 3 that's V11 an 807 (green wire) which is one of the IPA's - also removed a single blocking resistor on the cap of the same tube. Those are two 400 ohm resistors.

October 19, 2025 - Took the top off and will be taking the sides off so I can get to the wiring harness and work on rach individual module.

October 11, 2025 - Things that are working - filament power to all but the 100TH tubes, exciter (see below picture).  Not working - filament power to the 100TH's (tested external and filaments work), grid measurement and HV power - lots of work to do.

October 9, 2025 - Working on the high voltage issue and investigating why the 100TH's won't light up.  Tested the filaments on the 100TH's and they were fine.  Checked the filaments on the 3B28 rectifiers next - one of them the filaments would not light so I ordered two of them and they should arrive on Tuesday.  Also installed the new fuses.

October 8, 2025 - Making progress - got the unit powered up - replaced a 807 where the filament was not lighting, cleaned the relays and was able to turn on the filament power, exciter power and the plate power - initially the relay was chattering when I turned on the plate power but some good cleaning of a relay with Deoxit resolved the issue.  One remaining issue I need to explore is that the 100TH tubes filaments are not lighting.

October 3, 2025 - Got the BC-610 inside and got all the tubes installed - was missing a 5Z3 so I ordered one.  Also built the power cord on October 1st.

September 29, 2025 - Took some pictures of the inside of the BC-614-E,

September 27, 2025 - Replaced the screws in the bottom with stainless steel screws - the ones in the base were rusting and the ones holding the HV power supply in were temporary.  I ran out of black paint for the bottom - the brown is the primer.

Also found a box of nine of the correct power plugs - Hubbell 7224 - there may be a newer number (L2-20R) that will work as calling Hubbell they didn't have any info on this older one, but mentioned the new one and it looks promising.  For now I will use the older one.

September 22, 2025 - Here's the the power plug. I have ordered what I believe is the mate for the power plug.  I also received some additional coils and tuning units - more on those later.

September 21, 2025 - Got it out of the truck today.  When it was loaded on Saturday we discovered someone before previous owner I purchased it from had taken the bolts out that hold in the power supply in the bottom of the unit.  It fell forward and getting it back in before putting the base on took up most of the time unloading.  I also primed the base with Rust-oleum and painted then it black.  The BC-610-H is S/N 836.  The BC-614-E is SN 524.

 

September 20 - Picked this up today.

September 19, 2025 - the newest boat anchor.

The BC-614 - below.