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#v3 #ubitx #ubitx-help #v3 #ubitx #ubitx-help

 

After a couple of years of excellent performance, my ubitx V3 (last V3 batch with TDA2822 on socket) suddenly showed reduced receiver sensitivity and no-RF out on transmit. I have done the following tests:
- +15V on power transistor: OK.
- +12V on the main board: OK.
- total current drain on key-down: 0.6A.
- installed new firmware 1.20: OK.?
- power transistors warm-up moderately on long key-down.
- driver transistor war-up a bit on long-key-down.
- receiver works on all bands, but it has reduced sensitivity compared to previous performance.

I have no oscilloscope and no access to any lab during the present pandemia lock-down.
Any suggestion? There is anything I could chek to track the fault?
Thank you, bests
Jep, IZ0WIT
 

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Check the relays. If it¡¯s in all bands then check the T/R relay, if it¡¯s just some bands, check the filter relays. In either case bad relay contacts would account for both problems.?

Sent from an iPhone, don't ask whose.

On May 12, 2020, at 11:18 AM, Jep <giuseppe.cavarretta@...> wrote:

?After a couple of years of excellent performance, my ubitx V3 (last V3 batch with TDA2822 on socket) suddenly showed reduced receiver sensitivity and no-RF out on transmit. I have done the following tests:
- +15V on power transistor: OK.
- +12V on the main board: OK.
- total current drain on key-down: 0.6A.
- installed new firmware 1.20: OK.?
- power transistors warm-up moderately on long key-down.
- driver transistor war-up a bit on long-key-down.
- receiver works on all bands, but it has reduced sensitivity compared to previous performance.

I have no oscilloscope and no access to any lab during the present pandemia lock-down.
Any suggestion? There is anything I could chek to track the fault?
Thank you, bests
Jep, IZ0WIT

 

Hi,

Check the BNC antenna connector and be sure that especially the center pin has good contact with the center receptacle. If you have plugged/unplugged the antenna a number of times it could be 'tired'.

73,

Bill KU8H

On 5/12/20 2:18 PM, Jep wrote:
After a couple of years of excellent performance, my ubitx V3 (last V3 batch with TDA2822 on socket) suddenly showed reduced receiver sensitivity and no-RF out on transmit. I have done the following tests:
- +15V on power transistor: OK.
- +12V on the main board: OK.
- total current drain on key-down: 0.6A.
- installed new firmware 1.20: OK.
- power transistors warm-up moderately on long key-down.
- driver transistor war-up a bit on long-key-down.
- receiver works on all bands, but it has reduced sensitivity compared to previous performance.
I have no oscilloscope and no access to any lab during the present pandemia lock-down.
Any suggestion? There is anything I could chek to track the fault?
Thank you, bests
Jep, IZ0WIT
--
bark less - wag more
 

I have seen the K3 relay, the single relay on the left side fail.? While you are transmitting, tap that relay with a screwdriver handle. Measure the output and see if it pops up.? If it does then replace that relay.? It switches the power from the receive to transmit circuits.?

That circuit doesn't affect receiver sensitivity But band conditions have been spotty.?
--
73
Dave

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