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Author Topic: Heathkit HP-13 mobile power supply - odd noises from supply and radio  (Read 1836 times)
KC8MWG
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Posts: 122




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« on: July 19, 2015, 11:57:09 AM »

Okay, I replaced all the electrolytic caps in my Heathkit HP-13 mobile power supply. Haven't replaced the cracked 25-watt 4 Ohm power resistors yet - the replacements are stuck somewhere in Florida with a "shipping exception" problem, but I decided to try it out anyway. Plugged it into my HW-101 and connected it to a fully charged 12-volt deep cycle battery, and put the relay lead on the battery's positive terminal. Turned the radio on, the relay went "CLICK!", and I immediately heard a high pitched noise from the power supply - I guess it was oscillating, which is what it is supposed to do, but I also heard a "WOOOP...WOOOP...WOOOP...WOOOP" from my speaker, which gradually got higher pitched and slower paced as the radio warmed up, but never went away. It's only hooked up to a dummy load right now so no idea what reception or transmission is like. Any idea what might be causing the odd noises from the speaker? I don't get those noises when the set is being powered from the HP-23 A/C power supply.
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KA4POL
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« Reply #1 on: July 19, 2015, 09:53:16 PM »

It had been a good idea to measure the voltages before connecting to the rig. I know after a repair you usually are highly interested in seeing results. But replacing the resistors could be essential for the right function.
So I would assume the voltages are not correct and therefore being the reason of what you describe.
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K8AXW
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« Reply #2 on: July 19, 2015, 10:04:01 PM »

Re: POL.  Concur with Dieter.  Trying out a recently repaired piece of gear with some parts still defective really isn't the wisest thing to do. 

Unless of course, you just can't wait to repair any damage it causes.

After you get the resistor(s) and install them, I'd suggest checking ALL of the voltages before plugging the power supply into the rig.

BTW, I used this same power supply for some time many years ago.  It does sing from the oscillation but that's all.  You might also want to check the battery voltage as you try the power supply and especially when you eventually connect it to the rig.

This combination does pull a substantial amount of current.
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KC8MWG
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« Reply #3 on: July 25, 2015, 03:04:56 PM »

Okay, I replaced the resistors. I can't seen to be able to check the voltages, other than the 12v sources, since it won't turn on without the radio being connected. I STILL get the same whooping/oscillation noise in the speaker (which seems to change pitch and speed as I turn the radio's volume control up or down). Not only that, but when I put the rig on "tune", the relay starts to overheat and I have to shut the rig off quickly.

Out of sheer curiosity, I hooked up my 400 watt power inverter to the same battery and plugged my HP-23 A/C power supply into it, and the radio powered up fine, but there was some noise like an A/C hum in the speaker (which is part of the power supply unit). No idea if that can be suppressed or if that is just in the nature of power inverters.
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KD0REQ
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« Reply #4 on: July 25, 2015, 06:33:42 PM »

inverters of the saturation type generate lots of ringing with those square waves.  generally there are some tuning capacitors in the vibrator or oscillator circuits, on the order of .1 to .5 uF, that damp the ringing.  everything affects everything else in this type of circuit, so get a couple of caps in that general range on alligator clips, put a scope on the affected lead, and see if you can tune to the new parts' different characteristics. same thing with TV flyback circuits... there, the damping cap is a "critical safety component" due to its tendecy to not only keep the SCR or transistor from frying, but also keep the flyback from bursting into fire.  in fact, if the transistors in that HP-13 die, replace those caps first, so you don't blow the replacements, too.

you will hear some whistle or whine on audio circuits from almost every inverter circuit.  if they were true sine waves, like you get from professional inverters for things like mainframes (or the old BEST Power Ferrups inverters which had huge magnetic effects beyond the case from the inductive flywheel) you would not have noises out of the ordinary.

turn up any Heathkit SB radio of the tube variety, and you will get hum.  back in the 70s, the talk was turn up the audio until it hums, then take that down until it's not driving you nuts, and use the RF gain for volume forever more.
« Last Edit: July 25, 2015, 06:43:35 PM by KD0REQ » Logged
KC8MWG
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« Reply #5 on: July 25, 2015, 06:57:07 PM »

turn up any Heathkit SB radio of the tube variety, and you will get hum.  back in the 70s, the talk was turn up the audio until it hums, then take that down until it's not driving you nuts, and use the RF gain for volume forever more.
Only thing is, I don't get any hum when I plug the HP-23 into the regular house wiring, only when I use the inverter. Now, I can put up with that hum if it is ONLY in the receive audio - I've heard as bad, if not worse, on some of my old broadcast receivers (and that is AFTER I have replaced the caps; often depends on the original quality of the radio as well as how "primitive" it is...), but if it is likely to end up in the TRANSMIT circuits, that may be a problem.
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KA4POL
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« Reply #6 on: July 25, 2015, 11:22:54 PM »

Sorry to insist. You need to measure the voltages as the Heathkit assembly manual says.
On your replacement caps, did they come out of the junk box or did you buy them new. It always could be a bad ESR value that would exclude a cap from use.
Obviously the reason lies in the supply.
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KC8MWG
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« Reply #7 on: July 26, 2015, 05:10:57 AM »

I don't have a complete manual, which is part of the problem. It's a partial that is only a few pages long plus the schematic that I found on the mods.dk website. Doesn't help that I have a 1st generation HP-13, and not an A or B. My manual, such as it is, is for the A.

My caps were ALL brand-new. I do NOT recycle electrolytics, ever. Too many unknowns, there.
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W5RKL
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« Reply #8 on: July 26, 2015, 06:16:52 AM »

I agree, the resistance and voltage checks must be done before you attempt to power up the HP-13 supply again.

Since you do not have the complete HP-13 assembly manual then I highly recommend you purchase the complete assembly manual from a reputable source so you can refer to it. You will need the fold out pages that show how the supply is wired and how the interconnecting cable is wired!!!

The HP-13 connects to the HW-101 through a 11 pin round female connector. Pins 9 and 10 on the 11 pin round female connector are the HW-101's front panel Volume control ON/OFF switch, same as on the HP/PS-23 supplies. Therefore, you should be able to remove the 11 pin round female connector from the rear of the HW-101, short pins 9 and 10 on the round 11 pin female connector, and the HP-13 supply should turn ON.

The DC voltages required to operate the HW-101 which are the same as found on the HP/PS-23 power supplies, should be found on the round 11 pin female connector as follows:

Pin 1 Bias Voltage, -130VDC (adjustable by the bias pot on the right side of the HW-101)
pin 3 LV, 300VDC (determined by the connection of C7, D5, and D6 to the BLU/YEL (250VDC) or BLU/GRN (300VDC) to the power transformer's secondary winding
Pin 4 HV, 820VDC (final amplifier 6146 plate voltage)
Pin 7 Ground (all DC and filament voltage ground returns)

Use caution when performing voltage checks. The HP-13 has DC voltages that can KILL YOU!!!

Do NOT use a cheap $9 hardware store volt meter to perform the voltage checks. Use a good quality DVM/DMM that has a DC voltage range of at least 1000VDC!!

If you do not have the experience measuring the supply's DC voltage, find someone/ham who has the experience to help you. Do NOT do it if you have any doubt what so ever!!! Better to have someone else do it for you then to damage the supply or harm you in the process!!! Use some Common Sense!!!!

73
Mike W5RKL
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KC8MWG
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Posts: 122




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« Reply #9 on: July 26, 2015, 01:13:13 PM »

Well, I put an ad in the classifieds for a manual, but if any of you can direct me to a reputable dealer who might have one in stock that would be great. As for measuring voltages, I do have experience doing so. As I said, my main hangup is in not having a manual for this unit, just a schematic. As far as instruments for measuring voltages, I have a Heathkit V-7 "A" VTVM that is quite capable of handling up to 1,500 volts, so I am set there.
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KA4POL
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« Reply #10 on: July 26, 2015, 09:53:21 PM »

There is a very helpful Heathkit Yahoo Group.
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W5RKL
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Posts: 939




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« Reply #11 on: July 27, 2015, 05:01:36 AM »

Well, I put an ad in the classifieds for a manual, but if any of you can direct me to a reputable dealer who might have one in stock that would be great. As for measuring voltages, I do have experience doing so. As I said, my main hangup is in not having a manual for this unit, just a schematic. As far as instruments for measuring voltages, I have a Heathkit V-7 "A" VTVM that is quite capable of handling up to 1,500 volts, so I am set there.

You can purchase the complete assembly manual at vintagemanuals.com. Price for the HP-13/A/B range from $18 to $20 (click on the following link for further details)

http://www.vintagemanuals.com/search.php?find=hp-13

Their manuals are excellent. Some manual may have check marks in the assembly steps but the text, drawings, and schematics are quite clear. I have purchased a number of Heathkit manuals from them and everyone was in excellent condition, well worth the price.

73
Mike W5RKL
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WB6BYU
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« Reply #12 on: July 27, 2015, 04:29:02 PM »

I would also check the DC voltage on the battery while you are running it, as well as the voltage drops in
the connecting leads.  Lots of current there, even on receive.  They always seemed to run best when an
alternator was charging the battery.

Make sure there is some physical spacing between the HP-13 and the HW-101:  the DC supply can generate
quite a field around it that can get into audio circuits, transformers, speakers, etc.

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