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Author Topic: TE Systems Repeater Amplifier Not Working  (Read 15886 times)
WB2WIK
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Posts: 20595




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« Reply #45 on: February 18, 2013, 10:38:30 AM »

Tip about replacing this type of transistor (irrespective of part number):

Loosen the two machine screws (Allen type, usually, but may be Bristol or Spline or almost anything) that mount the transistor first, before attempting to unsolder the emitter or collector tabs.  This will make the thermal transfer ("heat sinking" effect) from tabs to the heat sink much less efficient, and allow the tabs to be unsoldered pretty easily.

If you leave the transistor firmly bolted down, it takes an awful lot of heat to unsolder the tabs, and that can burn the board or degrade the board and attached components.

When soldering in the new device, I just place the machine screws and turn them in but not fully tight, until after the soldering operations, and then fully tighten them -- for the same reason.

There is likely a tiny amount of thermal grease on the back (flat mounting surface) side of the transistor where it rests against the heatsink.  I'd clean that away, make sure the HS surface is very clean, then apply a small amount of "new" thermal grease on the backside of the transistor before placing it onto the heatsink.  The Wakefield white thermal grease works fine, but there are other choices.  Don't use much -- the layer of the grease should be very thin.

Based on the reported observations, it does seem like the driver transistor failed and the output transistors are still good.  And of course it's true the TE "Repeater" amps use no biasing, they're Class C and intended for FM use only.
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W4JST
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« Reply #46 on: February 18, 2013, 04:20:59 PM »

Thanks.

What do y'all think caused the driver transistor to open like that?
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KA5IPF
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Posts: 999


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« Reply #47 on: February 18, 2013, 05:22:26 PM »

Base open = Too much driving power, usually.

I would run about 5-10w of drive and shoot for 200-250 out. If you are driving it with a "regular" 2m radio realize it could have some overshoot at the lower power settings. It depends on the radio and how the mfg handled power control. Driving it with a 50-60w radio turned down may not work too well.

At the least I would pull the PCB from the heatsink and clean all the heat conducting areas and apply new heat sink compound.

Clif
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WV4I
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Posts: 136




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« Reply #48 on: February 27, 2013, 06:05:04 PM »

If this really is a model 1552, it will present a very high input SWR on 144-148mhz. If this is simply the "problem", then might be able to retune this amp back down into 144-148 using trim caps usually in input side. Had to do this with a 6m TE amp one time that someone had obviously adjusted for use outside 6m amateur band.

Meanwhile, I've got a model 1410G that may be sick, only 100w out, saturates at about 6w in as expected, thinking a final, if nothing else pans out? Pulls 27A as advertised however.
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W4JST
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« Reply #49 on: March 10, 2013, 06:51:58 PM »

I replaced the driver transistor and the amplifier seems to be working perfectly now.

Thanks everyone!

Thank you KA5IPF!

I appreciate it very much.
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WB0GAZ
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Posts: 31




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« Reply #50 on: August 18, 2013, 04:33:20 PM »

Related to the same model, so including in this thread:

I wish to add SSB bias to existing, working TE Systems 1452RA repeater amplifier. I'm not concerned about relays, switching, etc., but do wish to run the unit in linear mode (so I'd expect to add one additional input, to enable SSB bias.

The big heatsink will be a plus for some long duty-cycle operations I have in mind, so does anyone have reference to info on what components are needed? I gather schematic is not generally available, but perhaps someone knows what-goes-where.

Very tks!

Dave
 
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WB0GAZ
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Posts: 31




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« Reply #51 on: August 21, 2013, 02:13:59 PM »

Found useful information at:

http://www.ham-hyper.com
follow link: Articles Techniques
follow link: Modification des amplis TE-Systems VHF & UHF (2 articles) par F5DQK

or try:

/index.php?option=com_content&view=article&id=85:modification-des-amplis-te-systems-vhf-a-uhf-par-f5dqk&catid=41:amplis--preamplis&Itemid=78

Thanks to F5DQK Marcel!
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