[MRCA] Fwd: TCS 5 Transmitter

[Chris Bowne]

The receiver screen voltage circuit Robert described is the one that is switched off on transmit by the keying relay.  And Robert to put your mind at ease, my small keying circuit mod can be removed in a few minutes to restore the transmitter from "parts set" to "original" condition.  The small relay is strapped in with tie wraps, no holes were drilled and no installed components or wiring were removed.  Part of the reason I put the mod in was to minimize wear and tear on the original relays, especially when keying at speeds above about 15 WPM. I used the set a lot on CW and it definitely is a lot more pleasant to operate in the manual T/R switch mode,  And like I said, it still can be break in keyed by leaving the switch in the receive position.  The acoustic noise of the relays is not that bad, the real problem is the loud switching transient clicks in the headset audio.  Having a keyed side tone in CW like in the command sets and the GRC-9 would have been a good operating feature, always wondered why that was not included in the TCS system_

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Begin forwarded message:

> From: WA5CAB at cs.com
> Date: October 15, 2014 at 1:35:14 EDT
> To: aj1g at sbcglobal.net
> Subject: Re: [MRCA] TCS 5 Transmitter
> 
> Jeff,
> 
> I could supply the schematics all the way back to the original TCS (no suffix number).  But between the TCS and the TCS-15 (the last model) aside from minor cosmetic issues (like whether the transformers have the information stenciled or printed on a dataplate), there exist only the following changes, only one of which affects a schematic.
> 
> At TCS-6, the posts in the four corners of the transmitter and receiver were replaced by three handles.
> Up through TCS-5, transmitter and receiver front panel connectors were mounted on the outside of the front panel.
> At TCS-6, they were mounted on adaptor brackets so that one can remove the front panels without unwiring the connectors.
> At TCS-8, receiver IF and BFO transformers were changed from air core to iron core.
> During production of TCS-12, 13 and 14, the RF Ammeter on the transmitter was moved from the ground side of the variometer to the antenna post.
> 
> No other changes affecting schematics were made.
> 
> The most common cause of deaf receivers is that when operating one by itself on the bench (meaning not connected to the transmitter through the power unit), the tech forgets to jumper pins 2 and 3.  This leaves the RF, Mixer and 1st IF amps with no screen voltage.  I will remember this to my dying day because many years ago, I spent the better part of two days trying to fix a receiver without the jumper.
> 
> FWIW, I never considered the relay noise to be objectionable.  And would consider a transmitter so modified as a parts unit.
> 
> Robert Downs - Houston
> wa5cab dot com (Web Store)
> MVPA 9480
> 
> In a message dated 10/14/2014 20:50:04 PM Central Daylight Time, aj1g at sbcglobal.net writes: 
>> As I recall, there is a double pole contact on one of the T/R relays in the trasnsmitter that shifts the low voltage B plus between the receiver and the transmitter, it would normally be routed to the receiver in the key up condition.  I can't remember any other means of receiver muting being used.  I made a small modification to my TCS-12s sets that keys a small added 12V DC coil relay  with its contacts in series with the voltage feed to the MO and final screens to key the transmittter, when I  manually lock the existing T/R relays in the ttransmit state using the otherwise unused power switch on the transmitter front panel.   This eliminates all of the big antenna relay clatter while keying, the way I arranged it allows me to key everything as per the orignal arrangement with the power switch in the off condition, or when using a PTT mic in voice mode.  The power switch leads run directly to the transmitter multipin front panel connector, they normally were used to turn the transmitter portion external power supply on and off.  If perform that function with the power switches on the system remote control unit (RCU) that has power switches for the transmitter, receiver, and the spealer in the RCU, along with the speaker volume control.
>> 
>> 
>> Saw you also picked up a nice dual dyno TCS power unit at Deerfield - good luck with that, would be interested in finding out if the radios run any differently on it vs the big AC supply.  I have  (what was in 1988)  a brand new in the packaging  dual dyno supply to run my TCS-12s, think I bought it from a bunch August Link had for sale back then.
>> 
>> 
>> What did you have to do to get the TCS-13 receiver going, it seemed pretty dead to me!  Would be interested in seeing how you can get that front panel cleaned up!  
>> 
>> 
>> 
>> 
>> On Tuesday, October 14, 2014 8:12 PM, "w1aea at myfairpoint.net" <w1aea at myfairpoint.net> wrote:
>> 
>> 
>> 
>> 
>> 
>> Hi all  A TCS-5 Transmitter followed my Home from Near-Fest over the weekend,  As I go thru it and check things which are nearly inline I find that the thing Keeps My TCS-13 Rx  Muted all the time???  I expect there might be a small difference in this Earlier Transmitter Than the TCS-12 I'm using! But I don't seem to be able to find a   TCS-5 Schematic??  anyone have any ideas??  or a location of a Schematic for this Earlier  Tx??   This thing appears to be Unmolested??  thanks  Jeff W1AEA
> 
> 
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