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Author Topic: HW101 recieve a tad numb compared to the 303  (Read 3711 times)
KE4JOY
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« on: July 29, 2013, 02:50:42 PM »

Yes the 101's receive seems a bit numb compared to the solid state rig.

I am thinking this is 'normal' but I am also thinking the 101's receive might need a little bit of tweaking. Where is the first place I should start looking? Or am I just expecting too much from the old tubes?

ps; I have a slew of 6au6's to swap out but don't know which stage to look at first.
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AD4U
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« Reply #1 on: July 29, 2013, 06:44:06 PM »

I have a SB-101, SB-102, SB-301, and SB303 along with a HW-101 in my restored boat anchor collection.  When tested on the bench there is no practical difference in the receiver sensitivity among any of them.  A 0.1uV signal is plainly audible on each band on each one.

I would start with a complete alignment.  If still not satisfied I would check voltages at each test point as shown in the manual.  The tube type SB rigs are well known to have used resistors that go way high in value with heat and age.  High value resistors = low voltage and possible issues in receiver sensitivity.

Dick AD4U
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WB2EOD
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Posts: 221




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« Reply #2 on: July 29, 2013, 07:26:31 PM »

I have s soft spot in my heart for these old things.
Having worked on a few of these, I agree with the previous opinion. 
Alignment can be done with or without instruments using the crystal calibrator signal.  Either way, be sure to follow the instructions (which you should have before you touch anything).  Alignment is straightforward but due to the series/parallel configuration, must be done in the sequence specified.  I have seen cases where a realignment resulted in a significant improvement in performance.
In any event, hope you get it working and on the air.  It would be a shame to allow these relics to quietly die

73
WB2EOD

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G3RZP
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« Reply #3 on: July 30, 2013, 01:16:05 AM »

There aren't many HF receivers that aren't, in practice, mainly limited in usable sensitivity by the noise picked up on the antenna. Maybe things which are really glorified broadcast receivers like the S38 and maybe the S53 when you get above 10MHz, and some survivors from WW2 and before.

So I go along with the previous two posters.
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KE4JOY
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« Reply #4 on: July 30, 2013, 01:25:56 PM »

Gah... I hate to get into a re-alignment as mentioned the series tuned steps is a royal pain. Its working fairly well now and I am a tad hesitant to fix it. I went through the rig and aligned it a few years ago so unless something has given up in there it should be fairly close.

It can usually 'hear' anything the solid state receiver can hear unless its really weak but the meter deflection is quite different. An S9+ signal on the SS unit will barely get an S6 on the tube rig. Yes it can 'hear' the weak ones but they are much less 'present' for lack of a better word. I often flip to the SS rig to get a better copy. Speaking of the noise floor typically on say 20 meters the SS rig will show a good S3 of 'noise' the tube rig's meter hardly deflects.

One other thing I noticed is that the rf gain control seems to be over active. At the 2 oclock position (counter clockwise) about 30% of its 'throw' it pins the meter and mutes out all signals.
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G3RZP
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« Reply #5 on: July 30, 2013, 03:03:50 PM »

As far as S meter calibration on almost any rig  is concerned, figure that the 'S' stands for 'suspicious' and the meter is can be believed as much as either an HR VP or a politician - that means, 'no way at all!'
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KH2G
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« Reply #6 on: July 30, 2013, 07:56:20 PM »

Alignment is the court of last resort. After you've checked voltages etc and have determined there are no soft tubes etc then and only then should you consider alignment and only if you have the procedure for that particular piece of equipment. I have had to rework too many rigs where people started diddling to "see what would happen" Result - so far out it had to be brought to me and after I repaired the original problem, then I would realign to spec. (A lot of time spent that shouldn't have been necessary.)
Regards, Dick
KH2G
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KE4JOY
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« Reply #7 on: July 31, 2013, 12:50:16 PM »

Well I'll be darned. I opened up the rig to have a look and to check some resistors and was shocked at what I saw. The entire RF board (along with others) was coated in a greasy sticky mess  Huh Someone  Roll Eyes must have gone nuts in there at some point with what I assume was tuner cleaner.

It was filthy! Greasy grimy, cat hair, little chunks of ceramic, dust, bug parts, and what looked to be cigarette ashes. I even found a stray wire strand wandering around  Shocked I spent a couple of hours with small paintbrushes, q tips, and a grease cutting "Lysol all purpose" cleaner. I would dip the paint brushes into some cleaner sprayed into a cup and 'wash' small areas going back and mopping up with q tips. At least the rf board is clean now. I will go back and get the others later.

But, I replaced the tubes and put it back together. The performance seems to have increased to some degree. Still does not do as well as the solid state unit and the RF gain still acts overly aggressive.

I did find a few resistors that need replacing most notably a 220 ohm that ties the cathode to ground metered out at 300 ohms. Others were more or less within tolerance.

Had one panic moment when a wire pulled clean out, turns out it was a neutralizing stub  Grin
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AD4U
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« Reply #8 on: July 31, 2013, 03:00:00 PM »

Check the tube B+ resistors.  I think they are 33K.  Most are operating at or just over their 1 watt ratings.  If they read high, replace them with 2 watt resistors.  This is a very common problem with Heathkit SB and HW transceivers.  Also check your HP23 ps to make sure it is set for 300V and not 250V.  If 250V that will make receive not up to snuff.

Dick  AD4U

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KE4JOY
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Posts: 1384




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« Reply #9 on: July 31, 2013, 03:41:26 PM »

Oh the power supply is up to snuff It has been re-configured with the kit supplied by old heathkit parts

http://www.ultrawebb.com/OHP/HP-23D.htm and yes its set for 300V

It was checked out thoroughly after fabrication.

The B+ resistor for the RF amp is only 1/4 watt. It was slightly out of tolerance I plan to change it out.

I had a hellua time with the meter circuit until I replaced the 1W 100K with a 2 watt resistor.

Thanks for the tips
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K4JPN
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Posts: 22




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« Reply #10 on: August 03, 2013, 10:25:41 AM »

I ran into this problem years ago and found a simple solution. 

Pull off the relay covers and take a piece of typing paper or a brand new $1.00 bill and run it between the contacts 10 and 2 of Relay RL2.   The cover of the relays can be removed by pulling straight up.   Visit my web page http://www.thewinstonator.com/ham%20radio%202.htm for more tips and techniques on these fine old rigs.  The HW101, SB100 etc are all basically the same rigs.

73,
Steve K4JPN
http://www.thewinstonator.com/K4JPN.htm
 
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K4JPN
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Posts: 22




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« Reply #11 on: August 03, 2013, 10:28:50 AM »

One other thing to check is the B+ voltages, if they are low, check the 10K resistors, I have seen them go up in value on SB100, SB101etc, but not on HW-101.   I think Heath got a bad batch of 10K resistors years ago. 

73,
Steve K4JPN
http://www.thewinstonator.com/K4JPN.htm
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KE4JOY
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Posts: 1384




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« Reply #12 on: August 03, 2013, 01:19:43 PM »

I had cleaned those relays at some point back in the past but I went ahead and opened them up and cleaned them again.  Thanks for jogging my memory on that.

I got some dirt out of one of the relays but they were not too bad. But there seems to be some improvement though of course I don't have any quantitative measurement like I should.

I checked the 10K resistor on the B+ to the rf/if amp sections they were 'ok' at 12,000 ohms. I have not done the voltage tests yet as it scares me a little  Grin and the RF/IF sections are a real pain to get to because the foil side is populated with the driver/grid coils and barriers.

I also noted that there are no 6HS6's in there. There all subbed with 6AU6's. Don't think that would make too much difference though. Unfortunately I do not have any 6HS6 tubes in my stash.
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G3RZP
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« Reply #13 on: August 04, 2013, 12:47:33 AM »

The 6HS6 has twice the transconductance (gain) of the 6AU6, so it could make a difference. But if the noise increases when you plug the antenna in, you probably aren't going to miss much in the way of signals.
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AD4U
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Posts: 2186




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« Reply #14 on: August 04, 2013, 05:18:13 AM »

As previously posted both of my SB transceivers and my HW-101 all can "hear" a 0.1uV signal on all bands from my service monitor (IFR-1500).  The receive section in the SB and HW rigs is basically the same except the SB rigs use a slightly better crystal filter (6 poles VS 4 poles) for better selectivity.  I imagine one could put a SB filter in a HW without any mods.

As G3RZP said just because a rig can "hear" a 0.1uV signal on the bench does not mean all that sensitivity is beneficial on the air.  Atmospheric noise and lots of other factors often (usually always) make that level of receiver sensitivity not important especially up to the high end of the HF spectrum.

It would help if we knew what the actual receiver sensitivity of each rig is.  If the 303 is 0.1uV and the 101 is 5.0uV then you obviously have a problem.  However if there is only a very small difference as heard by ear, then I would not worry.  Knowing exactly what you are dealing with in specific terms will help us guide you further.

Dick  AD4U
« Last Edit: August 04, 2013, 05:40:53 AM by AD4U » Logged
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