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Author Topic: Pop pop fizz fizz oh what a supprise that is...  (Read 3603 times)
KE4JOY
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« on: April 25, 2011, 07:36:34 AM »

AC5UP will love this...

Transciever HW-101, PS HP23A (rebuilt), Reciever SB-303

So I tune around the band a little with the receiver and find some things of interest. I reach over and turn on the transceiver which 'bumps' and the ALC meter slowly starts to decline as normal when POP !... "what tha" fizzzzzz POP this time I saw bright flashes coming out of the HP23 and I dive for the power switch, but not before another POP POP! I cut the power and marvel in agony at the smoke coming out of the newly rebuilt power supply.

Now I rebuilt this PS a few months ago and has been working quite well actually. I figured a lizard or other pest had gotten up in the HP23. When I took it apart there was no immediate signs of damage. No exploded caps, no cooked resistors, no dead lizards. There is a thin protective cover which covers the holes for the now removed filter caps. I carefully pried that loose and was shocked to see water droplets on it! I turned the PS over to look at the other side and a few drops of water came falling out !

The PS sits in a window sill of my shed/shack. That window is 'cracked' open about 1/2" to let cables and grounding straps run through. The night before we had a hellacious thunderstorm with very high winds. I guess the wind was strong enough to blast water through that 1/2" gap right into the power supply !

Further inspection revealed a hot spot on the board where the resistor bridge comes together. A quick check and all the resistors were within tolerance.

I placed the PS out in the sun to 'bake' and dry out for about 6 hours. Put it back together and gritting my teeth powered it up. No popping, no fizzing, and output is what it should be. So I connect it back to the rig and YAY everything seems fine.

Power output is fine, modulation is good drive, more or less the way things used to be, with one exception.

The indication of the ALC at the meter in transmitt is very low compared to what it was before. Previously the ALC was nearly over aggressive and the meter showed good strong swings.

The power output acts like the ALC is working properly and signal reports over the air do not note any overdriving.

I'm still trying to figure out what one has to do with the other. Haven't really got into the metering circuit yet, just recently noted the meter acting out of sorts but since the rig seems to be operating 'normally' I'm not really hard pressed to fix it.

I am however 'fixing' that gap in the window  Cheesy
« Last Edit: April 25, 2011, 07:38:21 AM by KE4JOY » Logged
AC5UP
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« Reply #1 on: April 25, 2011, 10:27:21 AM »

INSTINCT


Instinct or innate behavior is the inherent inclination of a living organism toward a particular behavior.

The simplest example of an instinctive behavior is a fixed action pattern, in which a short sequence of actions, without variation, are carried out in response to a clearly defined stimulus. However, instinctive behaviors can also be variable and responsive to the environment. Any behavior is instinctive if it is performed without being based upon prior experience, that is, in the absence of learning. Sea turtles, newly hatched on a beach, will automatically move toward the ocean. A joey climbs into its mother's pouch upon being born.[1] Honeybees communicate by dance the direction of a food source without formal instruction. Other examples include animal fighting, animal courtship behavior, internal escape functions, and building of nests.

-more- http://en.wikipedia.org/wiki/Instinct


While behavioral scientists define instinctive traits as unique only to living animals I submit to the readers of this thread that every Heathshkit ever built has an instinct, like the Salmon of the great Northwest, to return to the place of its birth... In this case, your HotWire-101 has an overwhelming desire to return to a landfill. As it is written in the assembly manual of eternity: From ashes to ashes, dust to dust, landfill to 10 Meter SSB to landfill again, yea, verily, it shall be done, but never with acid flux solder...

The next time your PS-23 starts to sizzle on the windowsill, do the right thing: PUSH IT OUT THE WINDOW TOWARD THE NEAREST LANDFILL !!!

 Grin
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N3QE
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« Reply #2 on: April 25, 2011, 11:03:36 AM »

HW-101 can be, to put it in a politically correct term, "sensitive" to B+ voltage with respect to overall gain levels.

It's possible that B+ is correct when unloaded but that it's drooping a lot under load. Screen supply comes from B+. This can also apply to the HV droop. The HP-23A is substantially less droopy, when operating properly, than many other power supplies of its era.

One useful but unintended indicator is the OA2 voltage regulator tube's glow. It's normal for it to change in intensity a little when you go to transmit but it shouldn't be, for example, extinguishing. This symptom doesn't narrow things down a lot (problem could be in the HW-101, the HP-23A, or could just be the OA2 itself!) but it's a very useful indicator that something is amiss.

One way you know it's a true boatanchor: the glow of the tubes is a useful indicator of proper operation :-)
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KE4JOY
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« Reply #3 on: April 25, 2011, 02:07:00 PM »

Heh... maybe that was one time the Hot Water 101 lives up to its name.... anyhow.

I observed the OA2 like you recommended. Neat tip BTW.

The regulator that was installed had very little glow to begin with then extinguished when in tune mode. Oh boy may be on to something.

I got another OA2 and put it in there. Nice glow, dims somewhat when transmitting.

But... no change. On a whistle the transmitter develops nearly 90 watts but with the switch in the ALC position the meter barely even moves. I also noted that the Mic/CW level still effects the ALC as one would suspect Full scale at the 11 oclock position.

The rig appears to be acting just fine with good drive its just the ALC meter is wonky. Oh it works fine in receive I should add, it reads a little high but it always has.

Another thing I found while testing is that the low meter reading seems to be allot worse on 20 and 10 meters  Tongue and it actually acts normal on 80, 40, and 15.

I'm off to check the B+ under load... carefully  Cheesy
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N4NYY
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« Reply #4 on: April 25, 2011, 02:33:29 PM »

I no longer have to watch reality TV. KE4JOY posts are much more entertaining.
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KE4JOY
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« Reply #5 on: April 25, 2011, 02:57:34 PM »

I no longer have to watch reality TV. KE4JOY posts are much more entertaining.

Yea tune in for the next installment of "Keep it on the air"  Grin

If I dont mange to smoke the rig or myself measuring the HV.  Shocked

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AC5UP
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« Reply #6 on: April 25, 2011, 03:05:35 PM »

If I knew ya' better I'd buy ya' an anvil and a rubber mallet just to see what happens........................... Roll Eyes

(there is a profoundly old saying at the root of that comment)
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N3QE
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« Reply #7 on: April 25, 2011, 05:39:45 PM »

It's good that your OA2 doesn't go out any more with a new one.

Don't get too wrapped up in what the meter is in transmit or receive.

It's normal for ALC to kick in less as you go up in frequency esp. to 15M or 10M.

At some point you stop fixing the rig and just use it :-)
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W5RKL
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« Reply #8 on: April 26, 2011, 06:56:49 AM »

Tom (KE4JOY),

Are you saying that the ALC meter should "always" show a "constant" level of ALC during sideband transmissions and if so please explain why.

73s
Mike
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KE4JOY
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« Reply #9 on: April 26, 2011, 07:42:03 AM »

Tom (KE4JOY),

Are you saying that the ALC meter should "always" show a "constant" level of ALC during sideband transmissions and if so please explain why.

73s
Mike


No it is the opposite, the meter should move when modulated.

How do I explain this... the tighter the ALC clamps down the higher the meter reading. With no modulation the meter rests at or near zero, with modulation the meter rises to relatively indicate the amount of 'limit'. A strong whistle should indicate full scale as the ALC at or near full 'clamp down'.

My issue is that the meter moves (in alc mode) very little if at all on 20 meters which led me to think It might be overdriving.

Why it would act this way on only one band makes very little sense to me. Both the ALC and metering circuits are independent of the RF sections. The only clue I have is that the rig was set for 20 meters when I had the fireworks show. Still both the ALC and meter circuits don't really interact with the IF/RF sections.

I guess I will have to flip her belly up (again) and check the alignment.
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AC5UP
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« Reply #10 on: April 26, 2011, 09:41:07 AM »

On every SSB rig I've ever used the goal was to minimize any indication on the ALC meter, and that's according to the book. Basic concept is that the ALC pulls down the * RF drive when it's too hot and a properly adjusted audio level will show an occasional deflection of the meter only on voice peaks.

In practice most folks set their mic hot enough that the ALC is working on more than just peaks and the meter shows "modulation" almost all the time. This adds some compression (sounds louder and nastier) but as long as the ALC is working as it should the RF waveform will have no flat-topping or cause any buckshot splatter near your signal. Personally, I like to verify that I have enough mic gain to push the ALC too hard then back it off into the linear portion of the curve. That tells me the audio, modulator and RF driver stages are healthy and I should have a clean signal. I'm also not big on pushing a 100 watt rig to the max... Usually set them between 80 and 90 watts because it makes no significant difference on the other S-Meter and if the metering circuit is off I'd rather have it err on the side of not overdriving the finals.

Probably doesn't matter, but I like to think I may squeeze a few more hours out of the radio by operating it with a little extra headroom.

* Edited to satisfy W5RKL.
« Last Edit: April 26, 2011, 11:15:21 AM by AC5UP » Logged

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W5RKL
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« Reply #11 on: April 26, 2011, 10:38:46 AM »

Tom (KE4JOY)

ALC is a transmitter gain control voltage that acts in a similar fashion as a receiver AGC gain control voltage does.

ALC's is used to prevent over driving of the final amplifier.

Nelson (AC5UP)

You said

"Basic concept is that the ALC pulls down the mic gain when it's too hot..."

That's not true. ALC has nothing to do with nor does it have any control what so ever over the mic gain that controls the speech amplifier (V1A and cathode following V1B).

ALC is produced in the HW-101 when grid current flows in the final amplifier. Grid current flows in the final amplifier when a portion of the driver tube's RF sine wave positive segment causes the final tube grids to swing positive. The ALC voltage produced is then fed back over the ALC line to control the gain of Isolation amplifier V2 and IF amplifier V3.

Tom (KE4JOY)

You said with no modulation the ALC meter rests at zero.

That's not necessarily true. The ALC meter will rest at zero even with modulation applied from the microphone. Just because you don't see any ALC indication during sideband transmission does not always mean there is a problem.

Why the ALC meter doesn't display the same ALC indication on all bands is because of the driver's signal level being applied to the final amplifier is different on other bands. As I said above, the level of ALC, if any, is determined by the driver tube's signal level that is applied to the final amplifier. This is explained in the Circuit Description section of the HW-101 manual.

There is no need to have a constant ALC indication when transmitting sideband. If the ALC meter just barely flickers when transmitting sideband then that's fine. If the ALC meter jumps to mid or full scale when speaking in a normal voice level 1 to 2 inches from the microphone then the MIC gain is most likely set too high! If the HW-101 is working as designed, no problems, drive is good etc, and you speak in the microphone in a normal voice level with the gain set so the ALC meter just barely flickers above zero, that's the point of maximum RF output with very little, if any, distortion in the transmit signal. That's the MIC gain setting and ALC meter indication you should strive for regardless of the band you are using. It's not about how LOUD you are but how clean you transmit signal is.

73s
Mike



« Last Edit: April 26, 2011, 10:40:34 AM by W5RKL » Logged
KE4JOY
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« Reply #12 on: April 26, 2011, 11:15:18 AM »

Right I understand most of that Mike.

Thing is that the ALC meter used to indicate similarly for all bands until the power supply mishap. It sill does except for 20 meters.

What I don't get is that the drive and output of the final section appears to be fine at 20 meters so the driver should have adequate output but the meter does not reflect that.

BTW the meter actually rests slightly below zero (on all bands) with no modulation. Which is 'normal' according to the service bulletins. Its just a relative thing.

I will have better ideas once I check the alignment.
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