Re: IC7000 no HF Transmit
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I appreciate all the instructions and advice from Andrew, JD and James. ?
It has been a few days since I last did any testing. ? So far, I have found nothing that is causing the output power to be so low. ?
I did go back and check the DRIVER/FINAL IDLING CURRENT as defined in section 4-4 of the service manual.? The idle current is set to 2.5A for the driver and HF-1 and HF-2.? Then I checked the voltage at the base of each PA transistor.? I observed the following:
Q301 = 4.3V Q302 = 2.4 V
What can cause these to be different? ? I do see that the output signal at each drain is not a clean sign wave. ?(See attached). Then, the combined signal at the output of transformer L305 seems to show two out of phase signals.
Any suggestions?
Thanks again Tommy KF4RWG
I have done a little more troubleshooting around the LPF final filter section.? I unplugged the cable from the main board to the PA.? I set the freq to 14.2 MHz.? I separated the output of L305 transformer and injected a 14.2 signal into C327 and looked at ant1 with a scope.? When I pushed tx the signal is seen at a reduced level at ant1.? I also saw the signal reduce at the input when tx is activated.? The signal level was 7 volts and is reduced to 3.5 volts when tx is activated.
I also saw 0 ohm resistance of the tx path of the RL801 at tx.? I also saw 0 ohms resistance inward side of C327 and C972 at tx.
I just chose 14.2 but all the filter paths are similar.
Please provide comments and suggestions.
Thanks Tommy
20% high does not sound too bad!!
It is when they drop low and you lose 90% will be the issue.
73
Andrew
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On 30 Jan 2025, 20:28, at 20:28, "Tommy Wooten via " <kf4rwg=[email protected]> wrote:
>JD
>I think Andrew suggested that capacitors may be the issue.? There are
>two
>large smt capacitors in the filter section after the PA section.? I
>removed
>these and measured them.? The result is as follows:
>C327 = 942 nF
>C972 = 811 nF
>
>These are rated at 680 nF and measure 20 to 30% high in value.
>
>I will check other caps in the path before the driver.
>
>Any thoughts?
>
>Tommy
>
>
>
>
>On Wed, Jan 29, 2025 at 1:02?PM J.D. Barron via
><jeter.d.barron=
>[email protected]> wrote:
>
>> RL801 may not be making good contact. You can check the levels with
>your
>> scope. I would use SSB and whistle in the Mike for tracing to keep
>the
>> power dissipation low.
>>
>> On Wed, Jan 29, 2025, 11:51?AM J.D. Barron via
><jeter.d.barron=
>> [email protected]> wrote:
>>
>>> Take a good look at RL801
>>>
>>> On Wed, Jan 29, 2025, 11:06?AM Tommy Wooten via <kf4rwg=
>>> [email protected]> wrote:
>>>
>> JD
>>>>
>>>> I was able to access each of the relay leads from the top side of
>the PA
>>>> board.? I found that each relay had the 14VR supplied at the relay
>coil.
>>>> The voltage is 10.5V and falls to 9.2V when tx is activated.? I
>verified
>>>> that L1 thru L7 leads were 10.5V and dropped to 130mV (gnd) when
>activated
>>>> by the appropriate band selection.? PHT8 at RL801 acted same when
>tx is
>>>> activated.
>>>> All gnd readings were 130mV except RL941 read 363mV as an
>observation.
>>>> All relays seem to click appropriately when each band was selected.
>>>> I cannot access IC981 since it is on the bottom side of PA.? But
>from
>>>> the info above it indicates it is working correctly.
>>>>
>>>> This does not explain why I was able to see 6W at the output of
>L305 but
>>>> I see negligible power when it passes through the filters.? There
>must be a
>>>> short or open in path.
>>>>
>>>> No smoking gun yet!
>>>>
>>>> I won’t stop until I find the issue or tear something up.
>>>>
>>>> Thanks
>>>> Tommy
>>>>
>>>> On Tue, Jan 28, 2025 at 5:45?PM J.D. Barron via
>>>> <jeter.d.barron=[email protected]> wrote:
>>>>
>>>>>
>>>>> (PA 1) The RF comes from L305? through HF03 to RL-801 (PA 2)
>(changes
>>>>> from orange to blue and out through (A). to
>>>>> (PA 3) the bandpass filters. There are a pair of relays that have
>to be
>>>>> energized for each frequency band. The input relays are controlled
>by L1 -
>>>>> L7 (Bus line 3) from the (PA 3) Q980 - Q987 by the outputs from
>IC981.
>>>>> (Powered by 3R3V)
>>>>>
>>>>> 14 VR provides the operating voltage for these relays and the
>output
>>>>> relays. (At this point I have to say I have not looked long enough
>and hard
>>>>> enough to understand how the output relays are activated but they
>must be.)
>>>>> as each band is selected by L1 - L7 going low.
>>>>> VR14 comes from RL701 output through L981 and resistors R1002 (150
>ohm)
>>>>> and 1003 (180 ohm) (paralleled). This line also provides power to
>RL801
>>>>> which would also stop the RF power from getting to the bandpass
>filters
>>>>> HF03 (Orange) to A (Blue). If R1002 and R1003 were open this would
>cause
>>>>> this problem as well. One of the anti-flyback diodes shorted could
>take out
>>>>> these resistors
>>>>>
>>>>> I think that as each L1 - L7 goes low that low is transferred via
>the
>>>>> blue line to the normally closed contact on the relay below to
>ground on
>>>>> the unenergized relay (I think).
>>>>>
>>>>> I would verify that the VR14 voltage is present first and then -
>if
>>>>> present
>>>>>
>>>>> I would look for the L1 - L7 signals being pulled low by Q980 -
>Q987.
>>>>> end then If switching I would look to
>>>>> The outputs on IC981.
>>>>>
>>>>> I believe you will find the problem in this area as you are
>drawing
>>>>> current indicating power being produced (unless the current is not
>in the
>>>>> 1-3 Amp range in SSB no modulation idling current).
>>>>>
>>>>> Since the power is not going through L961 the FOR / REV (SWR)
>>>>> transformer and being read by IC060 (JFOR) the RF drive is going
>to the
>>>>> point of current limit and cannot be adjusted in any carrier mode
>with the
>>>>> power adjustment.
>>>>>
>>>>> Just my best guess without making some measurements, but this is
>where
>>>>> I would start.
>>>>>
>>>>> Good luck and best regards.
>>>>>
>>>>>? JD
>>>>> KE4MD
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>
>>
>
>
>
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