SS IPA in a Harris HT 5

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engineer
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SS IPA in a Harris HT 5

Post by engineer » Sat Jul 22, 2006 10:42 pm

Anyone had any dealings with the IPA in a HT 5. I've got a unit running about 75% power. I have never had one of these solid state IPA units with any trouble. According to Harris it is not field repairable? It looks like a couple of push-pulls in parallel. I wonder why it would not be repairable in the field? The IPA normally runs at 30 v, 6.5 amps. It's running at 30 v, 4 amps now. If those are 100 watt FET's the low current would point to a failure on one side of the combine point. I would normally expect to see an increase in voltage with a drop in current, but the IPA power supply regulator is a strange board too. Any thoughts or comments are welcome. I will buy you a cup of coffee!

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Post by genlock » Sun Jul 23, 2006 6:00 am

Transistors may have to be a matched set.
Send it back to Harris. They will send you a new board.
I have found them to be reasonable.

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Post by Cameron » Sun Jul 23, 2006 10:29 am

Another thing to check is the supply voltage from the IPA regulator (A3).
It is adjusted by a control on the auxiliary board (A2R2). The power to the IPA is highly-controlled. If anything doesn't look squirrely here, get Harris to do the IPA swap.
Speaking of IPA... make sure the mod of part 394-702-000 happened in this box. The original bridge rectifiers in this box were a bad batch.

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Post by engineer » Sun Jul 23, 2006 11:19 am

Cameron wrote:Another thing to check is the supply voltage from the IPA regulator (A3).
It is adjusted by a control on the auxiliary board (A2R2). The power to the IPA is highly-controlled. If anything doesn't look squirrely here, get Harris to do the IPA swap.
Speaking of IPA... make sure the mod of part 394-702-000 happened in this box. The original bridge rectifiers in this box were a bad batch.
A2R2 does adjust the voltage and increases output. For our TPO, the IPA usually runs 30 v, 6.5 amps. It is running at 30 v, 4 amps. A2R2 is working, but no increase in current, only voltage. I'm aware of board A3, so I'm going to look at it on a scope. The IPA supply has one filter cap, I believe C1, which is a 100 v, 3300 or 33,000 uf. The transmitter is 16 years old, so I may change the filter cap in the IPA supply. From what Harris has told me the screen caps also have a history of causing problems. Thanks for the input.

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Post by Cameron » Mon Jul 24, 2006 8:55 am

engineer wrote:
Cameron wrote:Another thing to check is the supply voltage from the IPA regulator (A3).
It is adjusted by a control on the auxiliary board (A2R2). The power to the IPA is highly-controlled. If anything doesn't look squirrely here, get Harris to do the IPA swap.
Speaking of IPA... make sure the mod of part 394-702-000 happened in this box. The original bridge rectifiers in this box were a bad batch.
A2R2 does adjust the voltage and increases output. For our TPO, the IPA usually runs 30 v, 6.5 amps. It is running at 30 v, 4 amps. A2R2 is working, but no increase in current, only voltage. I'm aware of board A3, so I'm going to look at it on a scope. The IPA supply has one filter cap, I believe C1, which is a 100 v, 3300 or 33,000 uf. The transmitter is 16 years old, so I may change the filter cap in the IPA supply. From what Harris has told me the screen caps also have a history of causing problems. Thanks for the input.
If I'm looking at the same prints, C1 may have already been replaced once - Harris has it at 40V.

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