I have this amp here, and I need to find out the pre amp section on it and what transistors are the correct ones for it, it transmits super, but no pre amp, here is some pictures ot it.
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TX EIGHT HUNDRED AMP
- Thread starter skybolt58
- Start date
In the fourth picture, There are (2) 3 legged transistors. one is for the key up, the other is the rx amp. Your pictures are pretty blurry, so I can tell which one is the rx amp. The easiest way to tell is to desolder and lift one leg of either transtistor. If the amp stops keying, then the other is your rx amp. usually the transistor closest to the relay is the keying transistor.
TX EIGHT HUNDRED
OK so it would be the one farther back. both are 3904's but I tried changing to 2907's but no rec butthere was tx, then I switched them back and when I turn n rec the little relay clicks but no rec. there is 2 47 uf 25v caps there inthat area? 4 4148's also I replaces all 5 4148's. there is also a 3906 on the other side of that bigger relay, you can see it a little in the 3rd pic down that bigger one is for the TX, that works fine,
OK so it would be the one farther back. both are 3904's but I tried changing to 2907's but no rec butthere was tx, then I switched them back and when I turn n rec the little relay clicks but no rec. there is 2 47 uf 25v caps there inthat area? 4 4148's also I replaces all 5 4148's. there is also a 3906 on the other side of that bigger relay, you can see it a little in the 3rd pic down that bigger one is for the TX, that works fine,
I have had A couple of them in the past, but never had to replace the keying or RX amp transistors so I really can not help you.
If you do a search using the "search" feature at the top of the forum, you will find several threads about these amps and several different owners that had/have that amp.
Search TX800 LA 800 TX 500 or LA 500 as they were built under several names.
A lot of people like that style of amp and look for them.
I did not care for them due to the small heat sink, and I do not like amps with built in drivers, but that is just me.
The guy that built them also built the Pirate And Super Cobra amps, but as far as I know he stopped many years ago.
There are no known schematics that I know of and I think one of the Guys here that went by Marshal Dillon bought all of remaining parts off of the guy, I think his name was Steve, when he got out of it.
This Topic pops up from time to time.
I have not seen him here on the forum for a long time.
I would give that a try, and then send them a PM/Email and see if one of them will get back to you.
We have members that are not here every day/week but have posted about the amp in the past.
Other than that, you will have to find some one that can troubleshoot the amp and see exactly what is not working in the RX circuity rather than just replacing parts and hoping for the best.
Good luck in your search.
73
Jeff
If you do a search using the "search" feature at the top of the forum, you will find several threads about these amps and several different owners that had/have that amp.
Search TX800 LA 800 TX 500 or LA 500 as they were built under several names.
A lot of people like that style of amp and look for them.
I did not care for them due to the small heat sink, and I do not like amps with built in drivers, but that is just me.
The guy that built them also built the Pirate And Super Cobra amps, but as far as I know he stopped many years ago.
There are no known schematics that I know of and I think one of the Guys here that went by Marshal Dillon bought all of remaining parts off of the guy, I think his name was Steve, when he got out of it.
This Topic pops up from time to time.
I have not seen him here on the forum for a long time.
I would give that a try, and then send them a PM/Email and see if one of them will get back to you.
We have members that are not here every day/week but have posted about the amp in the past.
Other than that, you will have to find some one that can troubleshoot the amp and see exactly what is not working in the RX circuity rather than just replacing parts and hoping for the best.
Good luck in your search.
73
Jeff
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TX EIGHT HUNDRED
Thanks for that info, I tried a lot of searches with no luck, there is no real tech around me within 200 miles or better, and they are not true techs just golden screwdriver turners like copper and H&Y techs. I will keep searching tho! or just do one part at a time?
Thanks for that info, I tried a lot of searches with no luck, there is no real tech around me within 200 miles or better, and they are not true techs just golden screwdriver turners like copper and H&Y techs. I will keep searching tho! or just do one part at a time?
Skybolt -
I run a TX600 on my base. It's the same as the TX800 in everything but name (and a couple of capacitor values). The receive preamp in these units has very low gain compared to other amps, and doesn't boost up the receive a lot. On my 600, it seems that the only difference when the preamp is on is that the green LED is lit. I bought it new, and it's always been that way. When it was a couple of years old, I took it to the builder for an upgrade and I mentioned the lack of receive boost. When I got it back, Steve told me that the preamp was working perfectly. So ... I figured it was just the nature of the beast. I bought it because I was told that it was a bullet-proof kick-ass amp (which it is), and the low-rent preamp never bothered me. 73s.
- 399
I run a TX600 on my base. It's the same as the TX800 in everything but name (and a couple of capacitor values). The receive preamp in these units has very low gain compared to other amps, and doesn't boost up the receive a lot. On my 600, it seems that the only difference when the preamp is on is that the green LED is lit. I bought it new, and it's always been that way. When it was a couple of years old, I took it to the builder for an upgrade and I mentioned the lack of receive boost. When I got it back, Steve told me that the preamp was working perfectly. So ... I figured it was just the nature of the beast. I bought it because I was told that it was a bullet-proof kick-ass amp (which it is), and the low-rent preamp never bothered me. 73s.
- 399
TX EIGHT HUNDRED (HELP)
Gee still no answer on what components consist of the pre amp on this Linear? someone must have one that works>? or are they all junk?
Gee still no answer on what components consist of the pre amp on this Linear? someone must have one that works>? or are they all junk?
I have that exact same amp. Mine has had the power cables replaced with 4 AWG wire. Otherwise looks the same. It's been sitting in my garage for over 15 years now. Never really had the itch to hook it back up again. Looking to get rid of it if anyone is interested.
Relax! A preamp in a mobile is useless, unless you like to hear the same noise at a higher level.
