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Author Topic: HW-101 S-Meter Left Pegging  (Read 4011 times)
N2PTP
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Posts: 3




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« on: October 09, 2013, 08:56:56 AM »

I have seen lots of posts here, but after replacing all resistors on the ALC board and the tubes, my problem persists.
I have used Bob's (AB1MN) voltage refrence sheet to look at my voltages and they are not well...
Would there be anyone Bob? who could give me a hand tracking down the root cause?
My measurements are on the following PDF
https://dl.dropboxusercontent.com/u/30791681/Heathkit%20Measurements%20-%20ab2g.pdf

thank you
Scott -AB2G
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KD0REQ
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Posts: 971




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« Reply #1 on: October 09, 2013, 09:59:28 AM »

I would say pull tubes until the meter drops, but the tubes in the SB/HW transceivers are wired in series.  this makes this sort of troubleshooting sorta bogus.

the meter is driven by the AGC line, backwards.  so someplace the AGC line is open or shorted so there is no voltage.  without the schematic in front of me, that's the path to redemption.

not impossible for dirty relay contacts to mung that up, also.  the fix is drop power and zero out the voltages, carefully pop the dust covers, and use a strip of coarse paper like rag paper with some contact cleaner on it to drag through closed contacts on all the relay points.  you will have to manually depress the actuator to clean the NO points.

while the usual suspects are every single one of the 22K B+ dropping resistors going up in value, I found so many, many half-watters out of spec in the HW100 I've got on the bench that it's not outlandish to think of replacing the whole assortment.

here's where a signal tracer can be useful... work backwards from the AF amp until you lose signal in the speaker.
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N2PTP
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Posts: 3




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« Reply #2 on: October 09, 2013, 01:11:42 PM »

Already cleaned the relays, 22K 1W I replaced first.
Pulled the V3 (1st IF Amp) and meter went normal.
I have already replaced the resistors on the ALC meter switch, tightened all of the tube sockets...
Oh and a previous fun time was pulling the VFO and rebuilding (repacking) the jackson drives.  The VFO was really hard to turn and jumpy.  That was a good time, but well worth it.

Signal tracer on the way...
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N4NYY
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Posts: 4799




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« Reply #3 on: October 09, 2013, 03:06:11 PM »

Already cleaned the relays, 22K 1W I replaced first.
Pulled the V3 (1st IF Amp) and meter went normal.
I have already replaced the resistors on the ALC meter switch, tightened all of the tube sockets...
Oh and a previous fun time was pulling the VFO and rebuilding (repacking) the jackson drives.  The VFO was really hard to turn and jumpy.  That was a good time, but well worth it.

Signal tracer on the way...

Google the service bulletins. I think there is one for a meter. May be your problem.
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N2PTP
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Posts: 3




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« Reply #4 on: October 09, 2013, 04:07:14 PM »

Good call.  I have them downloaded.  Not sure if I have tried these yet.  I found 3 that are applicable.
Fun for tomorrow.
Scott
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W5RKL
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Posts: 893




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« Reply #5 on: October 11, 2013, 12:02:38 PM »

The following voltage measurement were taken in my SB-100, very similar to the HW-101 so they should apply.

The voltages indicated in your chart for V3, V10, and V11 with no receive signal appear to indicate all 3 tubes may be gassy. The meter, if the needle rests below zero after a few minutes or so warm up, is a good indicator that the grid voltage has reduced to the point it may have gone "positive".

Are you measuring the grid voltage with a VTVM or a DVM/DMM? All the voltage measurements indicated below were measured using a Heathkit IM-11 VTVM with a 1meg probe.

The following grid voltages are with the RF gain set fully CW and the SB-100 connected to a 50 ohm dummy load.

Measure the grid voltage of all 3 stages after a cold power on state.

V10's grid voltage is approximately -1.55VDC in receive.

V11's grid voltage is approximately -1.55VDC in receive.

If monitor V10 and V11 grid voltage, in receive, after 3 to 5 minutes or so and the grid voltage decreases then it's quite possible the tubes are gassy.

V10 and V11's grid voltage, in transmit, regardless of the mode and whether RF is present or not, increases to -90VDC in transmit, biasing both stages to cut off.

V3 is one of the "common" circuits that's used in both transmit and receive. The same above settings apply.

V3's grid voltage in receive is approximately -1VDC.

V3's grid voltage, in CW transmit with no RF applied to V3 (MIC/CW LEVEL control set fully CCW) should be approximately -12.4VDC dropping back to -1VDC in receive.

V3's grid voltage, with maximum grid drive to the finals (95 watts output indicated on a watt meter) in CW mode will be approximately -2.6VDC.
 
V3's grid voltage, with no audio from the speech amplifier (MIC/CW LEVEL control set fully CCW), in USB and LSB transmit (PTT pressed), should be approximately +.4VDC

V2, isolation amp, grid voltage in CW receive should be approximately -12.4VDC.

V2, isolation amp, grid voltage in USB and LSB receive should be approximately -1VDC.

V2, isolation amp, grid voltage in USB and LSB transmit, no audio from the speech amp, should be approximately +.3VDC.

V2, isolation amp, grid voltage in CW transmit with no RF and the CW key pressed, is approximately -11.4VDC. Releasing the CW key and just before VOX releases the relays, V2's grid voltage will rise to -12.4VDC.

V2, isolation amp, grid voltage in CW receive (the MIC/CW LEVEL control set for 95 watts output after tune up) is approximately -2.6VDC.

V2, isolation amp, grid voltage in CW transmit with 95 watts output in transmit (MIC/CW LEVEL control set for 95 watts output), is approximately -2.4VDC.

73
Mike W5RKL





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K4JPN
Member

Posts: 18




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« Reply #6 on: October 14, 2013, 07:02:41 PM »

Check by replacement the 6AU6 at V3, also replace R-106 with a 33K 2W resistor.  See my web page for service bulletins and my mods for the HW-101/SB100 series rigs.  final thing to check is the voltages in this area, if you find any low, it is probably a 10K 1/2 W resistor.  Years ago Heath had problems with the 10K 1/2 W resistors.  I have never seen this problem on a HW-101, but have seen it on several SB-100 series rigs.  The following is the link to the service bulletins.

http://www.thewinstonator.com/ham_radio_2.htm

73, Steve K4JPN
http://www.thewinstonator.com/K4JPN.htm
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G3RZP
Member

Posts: 4713




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« Reply #7 on: October 15, 2013, 02:50:08 AM »

One thing to watch with 6BA6s and 6AU6s of Eastern European origin is that some of them tie the suppressor grid and cathode together internally - so if the suppressor grid is grounded, so is the cathode. Make sure it's a 6AU6 from somebody like RCA or GE or a Mullard EF94.
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KE4JOY
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Posts: 1381




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« Reply #8 on: October 15, 2013, 01:42:18 PM »

Check the variable resistor for the meter zero, its on the side chassis. Check to see if it hasn't gone open.
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