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Author Topic: Heathkit HW 101 will not transmit  (Read 5392 times)
KA7MPX
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Posts: 4




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« on: May 16, 2013, 03:25:38 PM »

Well here it is in a nutshell......

Picked up a super clean HW 101 knowing from the previous owner that it received great but would not transmit. I thought, no big deal, I had one of these as my first rig over 30 years ago and I can fix it. This is where the fun begins!

I have the original manual and have completed the resistance checks as indicated...all checked out ok. I have a Jackson 651A dynamic tube tester and have checked every tube in the rig....they all indicated good. I've been through the trouble shooting portion of the manual....have 850 volts B+ on the plates of the 6146B's and all tube heaters appear to be glowing when powered up. I have cleaned all the rotary switches, relays and boards. I have verified that both relays are closing when the rig is put into "TUNE" mode (and they do close), and yes I have increased the mic/cw level knob while in "TUNE" mode which has zero affect. I have checked the screws and nuts holding the boards to the chassis to make sure the connections are good. I can put the rig into "TUNE" mode and absolutely nothing on the output of the radio. I can plug a key into it and and when I key down I can hear the CW tone from the radio but the relays do not engage and hence no output. I can plug a mic into the rig and when I key it no output. I do not have a signal generator or a scope to try and trace things that way. I do not see any visual signs of burned, broken or damaged componets anywhere on the rig. The radio does receive very nicely and is very excellent shape....wondering if there are any Heathkit Guru's out there that might have a few suggestions of what else and where else I can look to see if I can cure my radios problem. I am aware of RTO and many others that work on these rigs but feel like I have been issued a challenge by the radio Gods to fix this one myself!

Thanks in advance for the help!

73
Russ
KA7MPX
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KG6YV
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« Reply #1 on: May 16, 2013, 03:43:48 PM »

Do you have screen voltage on the finals?  Without it your tubes are cut-off... 6146's usually run ~200V on the screens to get them to conduct.
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AB1MN
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Posts: 42




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« Reply #2 on: May 16, 2013, 05:43:19 PM »

Hi,

Do you see any grid current when tuning up?

You might look at the voltages on the 2nd TX mixer and Driver (located on the PC board with the tuning cap with two rubber belts. Here is a link to an Excel spreadsheet with voltage and resistance values for each of the PC boards. Look at the tab for the RF Driver and check the resistance values (make sure power is off and voltages discharged before measuring the resistance values) and voltages for V6 and V7.

https://dl.dropboxusercontent.com/u/49531316/Heathkit%20Measurements.xlsx               

Good luck,

Bob  AB1MN
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N3QE
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« Reply #3 on: May 19, 2013, 05:53:09 AM »

To key the relays in CW, audio sidetone (which you've already found) has to be amplified by the VOX amplifier (V17A 12AT7) and the Relay Amplifier (V12B 6EA8).

The T/R relay driver circuitry is illustrated on this page of the schematics: http://ad4c.us/Other%20assorted%20manuals/Heathkit%20HF%20and%20VHF%20radios_/HW-101a.jpg

If you have a RF voltmeter or a RF voltage probe I'm sure you can trace RF voltage levels in transmit to find the stage where they stop.
« Last Edit: May 19, 2013, 06:03:01 AM by N3QE » Logged
WB1FFI
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Posts: 19




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« Reply #4 on: May 31, 2013, 05:54:42 AM »

My brother and I built a HW 101 back in 1977. It would not transmit after assembly. He is an electrical engineer/ham and found an open coil and defective 40 meter crystal. So there were 2 bad parts in the kit. Once changed out, the unit worked great. Good luck with your troubleshooting.
73, Barry
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K8AXW
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« Reply #5 on: May 31, 2013, 08:38:08 AM »

Russ: Many years ago I built the Heath SB-102.  After assembly the receiver worked great but the transmitter didn't work at all. 

I beat my head against the wall for two weeks trying to find the problem, using the few pieces of test gear I had.  I finally gave up and took it to the local Vo-Tech school where the instructor (also a ham) let me use one of the school's oscilloscopes.  I found the problem in 10 minutes!  It seems that I had soldered the signal path to a ground pad instead of the input to the next stage.

A short story to tell you this.  Get access to a scope and along with the schematic, follow the RF.  Fastest way to find a fix!

Al - K8AXW
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AD4U
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« Reply #6 on: May 31, 2013, 08:55:07 AM »

I have restored LOTS of Heathkit SB and HW rigs.  Compared to most every other ham rig, they are simple to troubleshoot.

Did it ever transmit?  That is the first question to ask the previous owner.  Since it is "super clean" it is possible that the original builder could not get it working and just put it aside and bought another radio.  

That is exactly what happened with an absolutely mint SB-303 receiver I bought several years ago.  It was absolutely perfect with all 3 filters.  It looked like it just came out of the box.  The dial lights lit up, but it did not receive - nothing.

First thing I did was go through the assembly section of the manual step-by-step as if I were building the rig from a kit.  Carefully checking each step took no more than 2 hours.  I found two wiring errors late in the assembly process.  

Maybe the original builder was tired and worked too long at one sitting when soldering the wiring harness perhaps 35 years ago.  Both errors were where the original builder soldered the center conductor of coax carrying the desired RF signal to ground instead of to the proper pad on the circuit board.  As soon as I corrected the two wiring errors, the SB-303 came to life, I am sure for the very first time ever.

When you switch it to TUNE can you hear a low level carrier in an adjacent receiver tuned to the same frequency as the 101?  If so the low level multiplier stages are working.  If not the problem is backwards from the amp stages.

Go through the assembly portion of the manual step-by-step as if you were building the rig from scratch.  

Since you posted on May 16 and since today is May 31 (15 days) with no response, maybe you got it working.  If not none of us can give you any more ideas until we hear from you.

Dick  AD4U

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KA7MPX
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« Reply #7 on: May 31, 2013, 09:33:55 AM »

Thanks everyone for the input and information. I have still not found the issue with this rig. Dick, AD4U, I can hear a low level carrier on an adjacent receiver when the rig is placed into the "Tune" mode....hmmmmmmm. Without a scope I suppose I can narrow my search down to the final amplifier stage(s) and see what I can find. I'm guessing it's something simple. The rig did transmit before and even has a tag on the chassis from Heathkit dated 1980.

Thanks again for all the advice and I'll keep looking into it as time permints.

73
Russ
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AD4U
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« Reply #8 on: May 31, 2013, 10:23:56 AM »

Thanks everyone for the input and information. I have still not found the issue with this rig. Dick, AD4U, I can hear a low level carrier on an adjacent receiver when the rig is placed into the "Tune" mode....hmmmmmmm. Without a scope I suppose I can narrow my search down to the final amplifier stage(s) and see what I can find. I'm guessing it's something simple. The rig did transmit before and even has a tag on the chassis from Heathkit dated 1980.

Thanks again for all the advice and I'll keep looking into it as time permints.

73
Russ

That indicates that the multiplier stages are working and the problem (at least one of the problems) is AFTER the multiplier stages.  A simple trouble shooting test like that reduces the area you need to look.  I would spend my time looking around the 6CL6 driver and the 6146 finals.  Using a scope to "chase" the RF would be invaluable.  Also look for resistors that have gone WAY high in value or that have opened due to heat and or age.  I had to locate and replace 37 WAY out of tolerance resistors in the last SB-102 I restored

Good Luck

Dick  AD4U
« Last Edit: May 31, 2013, 10:33:39 AM by AD4U » Logged
KE3WD
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Posts: 5689




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« Reply #9 on: May 31, 2013, 12:17:32 PM »


I beat my head against the wall for two weeks trying to find the problem, using the few pieces of test gear I had.  I finally gave up and took it to the local Vo-Tech school where the instructor (also a ham) let me use one of the school's oscilloscopes.  I found the problem in 10 minutes!  It seems that I had soldered the signal path to a ground pad instead of the input to the next stage.


Al - K8AXW

That reversed ground lug problem was a Heathkit fiasco that apparently went on for quite some time. 

The terminal strip included with the kit, typically the two-lug strip that connected the coax from IF output to the AF section, was built backwards from the one in their pictorial. 

So if someone followed the way it looked in the pictorial, but did not notice that the Ground Lug was on the wrong side from the pictorial, the end result was a totally quieted receiver. 

Can't recall how many I troubleshooted for other hams where this was the only problem, but it included a LOT of HR-10 receivers for a year or two back in the middle 60s.  And, of course, a few other models as well. 

73
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ZL1BBW
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« Reply #10 on: May 31, 2013, 01:47:32 PM »

On the SB101 you operate crystal locked TX from a front panel switch, I recall from my MM days.  Make sure that is not the case here?
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ex MN Radio Officer, Portishead Radio GKA, BT Radio Amateur Morse Tester.  Licensed as G3YCP ZL1DAB, now taken over my father (sk) call as ZL1BBW.
K8AXW
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« Reply #11 on: May 31, 2013, 09:01:22 PM »

WD:  I was never aware of the solder lug problem.  In my case I soldered the RF lead to a PCB pad that I thought was the input to the next stage when in fact it was a ground pad.  The pad I was supposed to solder to was under the wiring harness!  Roll Eyes
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KE3WD
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« Reply #12 on: June 01, 2013, 05:15:21 AM »

WD:  I was never aware of the solder lug problem.  In my case I soldered the RF lead to a PCB pad that I thought was the input to the next stage when in fact it was a ground pad.  The pad I was supposed to solder to was under the wiring harness!  Roll Eyes

If you still have access to an assembly manual, check the pictorial to see if it is correct or not. 

Its been too many years and I can't remember which exact models were involved, apparently, though, that one IF coax connection thing was problematic and I do recall some where the circuit board coax connection was reversed as well.  However, once I knew about that particular situation, "dead receive after build" -- I rarely consulted manuals, would just look for the shorted to ground IF at coax - FIRST.  There were several years where it was so common to find.  That many seemingly careful assemblers in most other aspects were not likely to all make the same mistake. 

But anything is possible in kit construction troubleshoots.  I'll leave the war stories to those already published around the 'net. 

I don't know anything more about it other than what I've told from my own personal experience as the local ham club's goto guy when ham stuff didn't work, never contacted Heath about it or anything, such did not cross my young mind at the time, just rather enjoyed watching the faces on the mostly older guys when, after a quick look and use of the soldering iron, they heard the rush.  *grin*

It did become obvious to me that there were quite a few kit builders who had not much interest in how the things worked as versus getting the things to work.  I'm sure that some of them did not understand, even after the repair and my meager attempt at explanation. 


73
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W5RKL
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« Reply #13 on: June 06, 2013, 05:44:36 AM »

On the SB101 you operate crystal locked TX from a front panel switch, I recall from my MM days.  Make sure that is not the case here?

I think you are referring to the SB-101's front panel "OSC MODE" control switch (LMO-XTAL-AUX-1). The HW-101 doesn't have that switch.

If receive is working fine, as it appears from the initial posting comments, then that eliminates the Carrier Generator (USB, LSB, CW/TUNE) xtals, crystal filters, V3 first IF amp, band switch selected Heterodyne Oscillator and crystals, and the LMO, all of which are common circuits in both transmit and receive.

If closing the CW key in CW mode produces the sidetone in the speaker but the relays will not energize, check diode D201 at the grid of V12B. Relay amp V12B is working otherwise the relays would not energize in TUNE Mode and when PTT is connected to ground. PTT and TUNE Mode are wired in parallel, they both ground the cathode of relay amp V12B, turning V12B ON resulting in the relays energizing. The CW sidetone is amplified by VOX amp V17A and it's output is fed to diode D201 where it is rectified into a "positive" DC voltage that is applied to the grid of V12B, turning V12B ON, energizing the relays. An open D201 or if D201 is installed backwards, will prevent V12B from energizing when the CW key is closed. If D201 is installed backwards, the rectified DC voltage will be "Negative" and V12B will not conduct and the relays will not energize when the CW key is closed/pressed.

I would check the driver tube and final tube screen voltages in both receive and transmit. Relay terminals 3, 11, and 7, control the screen voltage to the driver and final tubes. Loss of screen voltage to the driver and final tubes will result in zero RF output. The relay that controls the screen voltage is the relay mounted between the audio board (right rear) and the final cage. A wiring mistake/problem at terminals 3, 11, and 7, will affect the driver and final tube screen voltage.

Another check is to place the meter switch to PLATE and key the transmitter either in TUNE Mode or by shorting PTT socket to ground. If the final tubes have positive screen voltage (approximately 275VDC) and normal Plate voltage (approximately 825VDC), the meter should indicate a rise above zero and adjusting the bias pot should allow the setting of the idling current (50ma, meter points to the triangle above number 3). If the meter remains at "zero" and adjusting the bias pot has no affect then the final tubes are cut off.

If the driver tube's screen voltage is okay but the final tube screen voltage is missing in transmit, check diode D901, it may be open or installed backwards.


73
Mike W5RKL


« Last Edit: June 06, 2013, 05:54:34 AM by W5RKL » Logged
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