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Author Topic: SB-102  (Read 16764 times)
KK4SWD
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Posts: 12




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« on: June 18, 2013, 06:19:23 AM »

I recently purchased a Heathkit  system. i  Now have the manuals for the Xcvr and Amp (SB-200) have a Cantanna dummy load, a mike is on its way. Will pick up some coax today, so soon I will have what I think is what I need to do a fire up. 

So are there any experienced Heathkit Guys that have any pointers as to starting this old radio, the condition of this radio is unknown.

All I have done so far is make the pwr cord, replace the two broken o-rings, and purchased a can of contact cleaner that is plastic safe, have not sprayed or cleaned anything.  I tried blowing the dust out by blowing on it but it seems somewhat attached, not sure if it belonged to a smoker or not the out side cabinet is clean.

So should I blow it out with my compressor, spray it with contact cleaner or just plug her in and try it as is.
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KE3WD
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« Reply #1 on: June 18, 2013, 07:36:35 AM »


So should I blow it out with my compressor, spray it with contact cleaner or just plug her in and try it as is.

I recommend doing that.  Deoxit into all switches and controls except for main AC power switches, leave them DRY to avoid problems from arcing at switchoff. 

With these older boat anchors, be prepared to have to change old electrolytic caps, carbon cop resistors that have gone out of tolerance, and with the Heathkits - touching up bad solder joints, tightening pcb board hold down screws that may be used as grounds, making sure that bandswitch mechanicals are still intact and working and index properly, at a minimum. 

Dirty/Dry controls can mask a whole lot of symptoms, can throw calibration way off in certain instances, the unqualified operator will often proceed to realignment in an attempt to cure - and the realignment, of course, is inclusive of the high resistance dry contacts, which throws the poor thing WAY off.  Clean and lube those controls first.  I have often seen rigs on my testbench fall right back into cailbration or darn near, just from the control cleaning. 


73
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KD0REQ
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Posts: 2404




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« Reply #2 on: June 18, 2013, 10:06:44 AM »

slap together a 1920 workbench first... power cord with the hot going through a lightbulb socket, thence to a cord receptacle.  put a 100 to 150 watt filament light bulb into the socket.  put that between the power supply and the wall socket.

dim to half-bright bulb, the power supply isn't failed hard.

bright normal brilliance, the transformer is shot.

you might not hear any stations with the radio on through the bulb, but if the capacitors were ready to blow up, they likely won't become rockets, either.  check the DC voltage... Heath power supplies were diode, not vacuum tube, rectified, and you should see half voltage.  now remove the probe, set the meter to high AC scale, reconnect, and slowly click down until you can read the ripple.  if it's more than a half to a volt on any DC supply, you absolutely need to recap before running the rig on full power.
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KK4SWD
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« Reply #3 on: June 19, 2013, 01:29:30 PM »

What does it take to use the Receiver part of this radio?  I fired it up and now want to listen to some thing.  Can I use some sort of wire to receive a signal, or do I need to fab a real wire antenna to see if I can receive on this thing and what freq would I likely hear some traffic? thanks don't ya just love the dumb questions newbies can come up with? lol thanks John
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KE3WD
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« Reply #4 on: June 19, 2013, 03:15:15 PM »

You should be able to receive stronger signals by simply attaching a random length of wire to the center of the antenna jack and stretch that wire out along the floor or maybe up on the walls. 


Even a few feet will work somewhat.  Longer the better.


Just be certain not to try to TRANSMIT into that piece of wire, that could hurt the transmitter circuits due to SWR mismatches and such. 

In most cases, just disconnect the Mic and toss it into a drawer. 




73
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KK4SWD
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« Reply #5 on: August 03, 2013, 04:34:45 PM »

Just got around to connecting the SB-102 to a cantenna DL and when I go to tune I get nota on the meter in PLATE.  I contact cleaned all switches and pulled tubes sprayed and blew the tube sockets, and cleaned the tub pins.

What is the next logical step locate a tube tester, or something else.  It appears that the filaments are lit best I can see.

Anyone have a suggestion or two? 
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N3DT
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« Reply #6 on: August 03, 2013, 06:00:06 PM »

I'm thinking you may need a bit more help than we can offer on this thread.  I would suggest getting in touch with someone locally that knows about boat anchors and get some training.
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KE4JOY
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« Reply #7 on: August 04, 2013, 08:07:08 AM »

No current on the plate could be attributable to dozens of things, bad power supply, relay contacts, open or way out of tolerance resistors, bad meter, bad selector switch, bad contacts on the wafer switches, and on and on.

Yes you need to find someone who is familiar with that series who can follow a logical trouble shooting path.

Also be VERY aware there are lethal seriously deadly voltages present in that rig. Poking around in there without knowing what your doing can result in serious consequences.

I 'sort of' know what I am doing and it still scares me to work on them 'live'.
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KAPT4560
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Posts: 558




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« Reply #8 on: August 04, 2013, 04:00:03 PM »

 The schematic should have the expected voltages listed next to the tube socket pins. Carefully check for the correct voltages at the power supply and move outwards. As stated, use caution as higher voltages exist in some sections.
There were numerous updates to make these transceivers perform better. I have a similar SB-101.
http://www.w7ekb.com/glowbugs/ModsEtc/modifications.htm
 The older silicone diodes were very expensive in the beginning and weren't nearly as good (they got leaky and high PIV ratings were difficult) or affordable as the ones we have today.
 After the mods, the rigs are much nicer and more stable to operate.
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KK4SWD
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« Reply #9 on: August 04, 2013, 06:11:40 PM »

Well, I started checking resistor values and found about 5 that were off by over 50% and many more off sum.  So I'll start with the ones way off and work my way down the list.

Also found the expected voltage chart, so I pulled the unit out of the case and will have that to go on after all bad resistors are replaced.

Also after removing unit from case, found a swollen electrolytic cap that I'll be replacing.

Question, should I replace any resistor that is off more than 10%?  The tolerance band is silver.

Also found the V 18 tube was not lit (no filament) so I'll replace the bad resistors and cap. then check for filament voltage and go from there.   

The expected voltage chart should be a big help.

I expect this process is like fixing leaks, start with the big leaks and then the little ones will show up.

Thanks to those that offered places to start, I suspect some day I'll have this baby singing like new.
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N3DT
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« Reply #10 on: August 04, 2013, 08:13:07 PM »

I'd replace any resistor that was 10% or more.

I didn't mean to be rude, but I felt there was so little information about your problems, it was really hard to address.  It sounds like you are on the path to fix it, like you say, start with what you find and proceed with the smaller stuff.

I'd replace any/all electrolytics.

Let us know when it's running good and hope to hear it on the air.
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AD4U
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« Reply #11 on: August 05, 2013, 05:42:54 AM »

The last SB-102 I restored had 37 resistors that were more than 50% out of tolerance and had to be replaced.  Some 100K resistors in the metering circuit and one or two around the 6146 tube sockets were completely open.  It has been well documented that some SB gear had resistors that did not age well.

This rig is approaching 40 years old.  I would replace all electrolytic caps.

Dick  AD4U
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G3RZP
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Posts: 1321




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« Reply #12 on: August 05, 2013, 10:45:25 AM »

Most carbon comp resistors of that age will have moved, some more than others. A few years back, I opened the two sealed polyethylene bags containing a 4k7 5% 1/4 watt carbon comp resistor complete with its NATO stock number label. It was packaged in 1963 and was 25% high in value.
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KK4SWD
Member

Posts: 12




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« Reply #13 on: August 05, 2013, 09:04:44 PM »

Just found a BIG leak,lol a open 7 watt resistor that reduces down 350v 2500ohms I think it was 350v into the resistor and notta coming out...
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K8AXW
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Posts: 7042




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« Reply #14 on: August 05, 2013, 09:45:12 PM »

NEEDONE:  JOY's suggestion of getting help was right on, however, it looks like you're doing pretty good on your own!  Very good.

I think some good advice for you at this time would be to continue checking, measuring and  expect to spend a great deal of time with this rig to get it back up.

Be patient and have fun.  What you are doing just might be more enjoyable than actually operating.

BTW, I build an SB-102.  There are 1,619 parts in it...counting all hardware.  While far from state of the art, you'll find the 102 a fun piece of gear.  I had a great time with mine and sometimes wish I had it back.

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A Pessimist is Never Disappointed!
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