TCS 12 Collins

[ve3lyx]

As noted I have my transmitter finally. It seems good although I have not yet applied power. I think today will be its lucky day. No visable damage and no funny smells. I did not get the cabinet with it but I have a friend who runs a high end Sheet metal business. I think he can copy it. I always believe if it can be made once then again should be possible.
BTW we were talking about ARC5 Txs and the modulator I use. I have been using it it most of last week on 80M with no complaints so it is practical anyway.
donVe3LYX

[iu1dek]

Hi Don, follow this one on ebay.UK....for cabinet and other spare parts.....http://www.ebay.com/itm/291959827222?_t ... EBIDX%3AIT
73 filippo

[ve3lyx]

Thank you so much.
I powered it up today. It works fine on Cw keying through the PSU set up that came with it. But no connection for a mic. The Key/mic jack has three connections. Grnd, key and mic but I am not sure if the mic is the tip or the middle contact. I would prefer a separate jack for the mic.
donVe3LYX

[roberto burdese]

Ciao Don, Tip is the PTT, Ring the MIC, (carbon). It needs a very fresh cartridge, because there is no mic amplifier. "BR"

[ve3lyx]

Yes I have some very good ones. I use them on my one tube pre1929 rig for phone contacts. So i wired up the Mic lead from the connector. I see beside it is audio grnd. What is that for since the circuit may already be grounded. I can trigger the relays with the key but perhaps that is wrong. I am going to have to print the manual. I need to look at the circuit. Takes me too long on a computer file to find it.
donVe3LYX

[ve3lyx]

I got it! Just got it working. Probably wont sleep. ;>)
donVe3LYX
Tnx Roberto for all your help on both the rx and tx

[ve3lyx]

There is a gurgle or sound on the AM when monitored. I suspect the 12 volt supply is not clean enough for the carbon mic bias and some of that is bothering the mic. My gut temptation is to rewire the mic circuit for battery bias but I hate to mess up an historic radio. I have a HD 12 volt regulated supply as well as a large computer supply (12v and 5 volt) I may try supplying the heaters with one of them to see what difference that makes. Also I have been told that the set only runs one PA tube on AM and two on CW. Is that really true? Seems odd to me. Why would they do that? Sometime I am going to have to find a schematic for the set.

[roberto burdese]

Ciao Ron, I suggest you not to remake the microphone circuit. The microphone picks up the supply from the modulator cathode current. I confirm that in telephony, works one valve, while in telegraphy operate two valves. The reason for this choice you have to ask "ARTUR COLLINS" !!! Follow a couple of diagrams. Have a nice day.Roberto."BR"

[ve3lyx]

Thanks Roberto. You have been a big help. I was able to fix it this afternoon. I had thought it got the bias from the heater circuit. Cathode is correct and that is no problem. I reworked the PSU today. Some repair and some changes. The single Valve ops for AM bugs me. My 19 set had a built in hobble as well on AM. I discovered a work around and now get more then double the output on AM with no inside work or soldering. Been using it so for over a year now. I believe they wanted to limit distance of transmission on phone since it is so easy to copy and anyone can understand it and could inadvertently give away location and plans. CW requires a radio man in most cases so is a bit stealthier. Anyway I am pleased to be using it. Thanks again for the help. I see the CW/Voice switch drops one PA tube filament (outboard) and adds the modulator tubes filaments. MMMMMMMMMMMMMM!
donVe3LYX

[ve3lyx]

I had a successful QSO this afternoon with the rig. Got a very good report. All voltages seem good. I used it to drive my twin 811A amp so I would have enough power to get some distance. Thanks for all the help. I am probably going to try AM with both PA tubes going but right now I am just going to enjoy it as it was originally produced. I was on 3705 with WB2NEW and KA2J.
donVe3LYX