Marine Radio Transceiver repair.

[HellasTechn]

Good day!

My father had this old Marine radio transceiver. The brand is : Lear Operations Research & Development Corp. and the model is XT700. I guess it dates back to the 80's.

when power is connected it turns on, display is ok, channel selector works but squelch, volume dont work. Also it can not receive or transmit. When TX button is pressed nothing happens.

I opened it up and by visual inspection i found a cracked c2407 transistor. I can not find a new one anywhere so i wonder which would be a siutable substitute?

I guess i will have to remove and test all semiconductors on the board.

Any suggestions ?

P.S.
I found no info about it on-line based on brand and model.

 

[Heliman]

2sc2407 is the same as C2407

 

[shrtrnd]

This won't be your only potential problem, but the transceivers of that era would blow the output transistor if you
keyed the transmit mic with no antenna installed. So that's one thing to be aware of.
Sounds like you have other problems as you have no(?) volume control for receiving.
Sounds like you've had it opened already to look for physically damaged components (?)
I'd be looking at you power supply capacitors, and then the power semiconductors first, then go from
there if you still have problems. Remember not to key that transmit button without an antenna attached.

 

[HellasTechn]

2sc2407 is the same as C2407

Yes. still i have not found where to buy it from or an alternative.

This won't be your only potential problem, but the transceivers of that era would blow the output transistor if you
keyed the transmit mic with no antenna installed. So that's one thing to be aware of.

Yes and that is what probably happened.

Sounds like you have other problems as you have no(?) volume control for receiving.

volume does not work but i think that it is just not receiving anything that's why.

Sounds like you've had it opened already to look for physically damaged components (?)

I opened it up and by visual inspection i found a cracked c2407 transistor.

Yes

I'd be looking at you power supply capacitors, and then the power semiconductors first, then go from
there if you still have problems. Remember not to key that transmit button without an antenna attached.

That sounds right. I will.

 

[HellasTechn]

I found a bad 2sc1971 mitsubishi power transistor. i looked on e-bay and found tons of really cheap but fake 1971's. I have no idea if they work or not. It is virtually impossible to get an original one since they are obsolete since 1984 or 1986.

 

[HellasTechn]

With DR. 73's de Edd guidance, i have also discovered a burned rf choke which i have replaced and a cracked diode which has no marking on it.

 

[Bluejets]

These (2sc1971) claim to be genuine Mitsubishi....... although, of the many claims about dilutie gear from Asia being cowdung, I've never seemed to have had any problems with the stuff.

http://www.ebay.com.au/itm/2PCS-RF-...128354?hash=item2ca45d2362:g:LuAAAOSwMmBVwJK7

 

[HellasTechn]

Well i have already ordered this one:
http://www.ebay.com.au/itm/161784105720?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

I know they are counterfeits but hopefully they work.