Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1] 2 3 4 5 6 ... 8 Next   Go Down
  Print  
Author Topic: Got a "technician special" SB-101 on the way -- what to expect?  (Read 8059 times)
KX4QP
Member

Posts: 404




Ignore
« on: March 25, 2019, 04:37:30 PM »

I won the bid a few days ago on a Heathkit SB-101 "technician special" -- seller says it powers up but has no output.  I don't yet have a power supply, so I won't be able to do anything with it when it arrives, but what kind of things can I expect to need fixing?  The photos don't show any obvious smoke marks or physical damage.

Obviously, I'll need to first check that the tubes are heating; I can check filament continuity with my multimeter, but I have no other means of testing tubes at present.  I'll try to ask around at my next club meeting, see if anyone has a tube tester.  Beyond that?
Logged
K8AXW
Member

Posts: 7042




Ignore
« Reply #1 on: March 25, 2019, 05:09:14 PM »

While trying to obtain a power supply, get an assembly manual for the 101.  Start on page one of the manual and "rebuild" the unit.  Check for mistakes, poor solder joints wires that had obviously were hot sometime in the past.... and modifications.....which if found, should be eliminated.

You obviously understand the tubes need checked.  All electrolytic caps should be replaced....no if ands or buts.  Another thing while "rebuilding" the unit  is to check the value of the resistors.  The old carbon resistors used in the Heathkits are notorious for changing value with age.

Finally, look upon this as a labor of love and not just something to do on a Saturday night.  It will take time and patience but you can have a great deal of  fun with this old rig both restoring it and using it. 

Of course the real fun is when you first power it up and it makes noise!
Logged

A Pessimist is Never Disappointed!
AA4PB
Member

Posts: 15067




Ignore
« Reply #2 on: March 25, 2019, 05:12:07 PM »

Here's one guy who went through the process: https://www.radioremembered.org/HW-101.html
Logged

Bob  AA4PB
Garrisonville, VA
AC2EU
Member

Posts: 1505


WWW

Ignore
« Reply #3 on: March 25, 2019, 07:17:48 PM »

Out of the Hallicrafters "frying pan" and right into the heathkit "fire", eh?
A "technicians special" without a power supply even scares me!
Technician special is usually a euphemism for a unit that everything has been messed with, burned up and cut out.
I hope it's not one of those.

GL!
Logged

KAPT4560
Member

Posts: 558




Ignore
« Reply #4 on: March 26, 2019, 01:15:04 AM »

 As stated, open it up and evaluate what you have. I was given an SB-101 station ensemble by a neighbor who's brother was SK.
 The plastic dial drive was broken which I was able to repair. Cleaning controls and switches. Check solder joints, general workmanship and tweaking tube socket contacts.
 I went through the factory service bulletins to make the xceiver the best it could be. It is an attractive, well-tempered rig:
https://www.nostalgickitscentral.com/heath/heathkit.html
« Last Edit: March 26, 2019, 01:18:24 AM by KAPT4560 » Logged
KX4QP
Member

Posts: 404




Ignore
« Reply #5 on: March 26, 2019, 02:12:36 AM »

Old caps and resistors, check.

Where does one buy relatively large resistors these days?  All the ones I've found on "public" sources like Amazon are 1/8W, or even smaller (and useless for this) SMD parts.  I recall seeing what looked like 1/2W or even 1W parts inside the Hallicrafters I have, and that isn't built to transmit 100W.  For that matter, same question applies to higher voltage rated electrolytics -- I bought an assortment and they're all tiny, and rated around 12V give or take.  Great if you're recapping a 1970s vintage transistor receiver; not so useful if you might need to handle 800V for the B+.
Logged
VK6HP
Member

Posts: 553




Ignore
« Reply #6 on: March 26, 2019, 03:39:32 AM »

When you get your HP23 power supply make sure you do the electrolytic capacitor update on that as a priority.  I bought one of the upgrade kits which fits a PCB to the chassis and allows the easy and neat use of modern high voltage capacitors (which are readily  available BTW, but not always in the original form factor or packaging). Antique Electronic Supplies is one good source of look-alike can caps, and many other useful bits and pieces.  Make sure you get a power cable with either the transceiver or PSU; it'll save you time and money in making one.  Check that it's wired for Heathkit connections as a few have Collins pin assignments.

As others have mentioned, it's worth being systematic about resistor checking as a fair percentage will be out of spec. My SB-102 restoration radio needed about 1/3 of the resistors replaced.  The Heathkit are easy radios to troubleshoot and you can work systematically once you get the set alive.  The manuals are also freely available from Web sources; ignore those that want to charge you for them.

I would advise a check of the LMO as soon as you have a functional receiver.  If the LMO jumps or warbles, you have a relatively major overhaul ahead of you, although there are some good Web guides to the required mechanical and electrical steps.  As a start, tune through the calibrator and observe whether the note changes smoothly, or jumps slightly with tuning.  Also, leave the calibrator tuned to give a few hundred Hz beat and listen for jumps or warbles over a period of an hour or so.  There will be some slow drift but jumps are what you're listening for, and hoping not to find.

There are a variety of service bulletins and hints on the Web but my SB-102 was pretty easy to bring back to full spec, although the driver and PA tube had just been replaced by the previous owner in an attempt to find missing RF output.  He'd missed the real fault, which was high value plate resistors in the carrier generator, and in a transmit mixer stage.

You can get all the half watt resistors you need from the usual suppliers, although they may be physically a fair bit smaller than the originals.  In most places bigger wattage carbon types can be substituted with any modern metal or carbon film equivalents although, for resistors around tube PAs and similar stages, I use more transient-overload-tolerant ceramic composition types if the carbon types are not to hand.

The Heathkit PCBs and associated grounding arrangements are not great, so at the very least tighten all the mounting and grounding screws.  Check also that you have sufficient range in setting the dial zero pointer as one of more heterodyne oscillator crystals may have drifted well out of spec.  In my case, the 40 m crystal needed replacing and I ordered a new crystal from a local supplier. Anecdotally, that crystal is most prone to problems so I elected not to risk an eBay used part.

My radio was in pristine cosmetic condition and, after quite a few hours of work, it really came up well, sounding good in both transmit and receive.  It even looked passable on my Collins shelf!  However, a keen collector saw it and decided he had to have it, so it's gone to a good home and still sounds great every time I hear him on it. 

Enjoy your radio!

73, Peter.



Logged
AD4U
Member

Posts: 2543




Ignore
« Reply #7 on: March 26, 2019, 06:48:42 AM »

I have rebuilt several SB 101 and SB 102 rigs. Apparently Heath used poor quality resistors in many of these rigs. Over time many if not most went very high in value. Especially those in HV circuits. The last SB 102 I rebuilt had 37 resistors that were more than 2X their value. Several were way high or open.

When working right the SB rigs were good rigs. I have 3 of them that work "right". They are fine rigs.

Good luck.

Dick AD4U
Logged
KE4OH
Member

Posts: 234




Ignore
« Reply #8 on: March 26, 2019, 07:09:24 AM »

1. Replace the 4 electrolytic caps in the SB-101.
2. Replace all caps in your power supply. Cheap if you source them yourself. Good replacement kits available from several sources, at a price. Make sure your power supply is wired for or switched to (depending on model) 300v for the "low high" voltage.
3. Get a screwdriver and pliers and tighten *every* *single* *screw* in the chassis. That includes where the PC boards mount to the chassis as well as all lugs, brackets, etc that attach to the chassis.
4. Look and see if the thing has been obviously modified. Common mods were various schemes to drive a frequency counter. Personally, I reverse all mods that I find before I power up. Others will advise you differently. I have found mods where PC pads have been cut with a Dremel, etc. I bridge those by soldering across them with a bare wire.
5. I don't think it's particularly necessary to test tubes before initial power-on. But do make sure the correct tubes are in the correct sockets. A tube tester in not necessary in any case. Bad tubes are the least likely thing to be a problem for you.
6. I also don't think it's particularly necessary to test (and replace if necessary) all the resistors before initial power-on. After you get the thing powered up, you may find some things don't work quite right (like S-meter, etc). That's the time to start looking for high-ohm resistors that have drifted way up in value. Do, however, look for burned resistors and replace those immediately. There are 2 big wirewounds on the audio board. These are prone to failure.
7. Clean *all* switches and pots with your favorite spray juice. I like Deoxit. Others will be horrified. Don't forget the  slide switches underneath that switch the SSB/CW filters.
8. Be prepared to pop the covers off the 2 relays to clean the contacts. May need cleaned, may not.
9. Get needle-nosed pliers. Grab *every* wire right where they are soldered and shake them. Re-solder as necessary.
10. Look everywhere for fly leads and whiskers that might be shorting something.
11. Look for lousy/questionable solder joints. Re-flow as necessary. When in doubt, get your solder out!
12. Depending on who built it and when, you will have 0 - 3 rubber drive belts to replace. They are just common o-rings you can get a a hardware store. Several sources on the internet also have them for sale.

Download a copy of the manual as well as all Heathkit factory service bulletins. The bulletins are pretty much the same for HW-100/101 as well as SB-100/101/102.

The very good TRW LMO may need some attention. They tend to get jumpy with age. There are two pretty simple fixes that will take care of it (cleaning the vernier mechanism and making a grounding improvement). Easy to find on the interwebs.

The SB-101 is complex, but don't let that intimidate you! These things were meant to be built and maintained by average folks. Plenty were built successfully by teenagers. You can get help here and on that other ham website.

Once you have everything in shape, you will have a very good transceiver indeed. They were well-known then and now as the "poor man's Collins". For very good reason. They are very, very good radios.
Logged

73 de Steve KE4OH
KE4OH
Member

Posts: 234




Ignore
« Reply #9 on: March 26, 2019, 07:11:41 AM »

Old caps and resistors, check.

Where does one buy relatively large resistors these days? 

Antique Electronic Supply, Mouser, Digi-Key, and others that escape my memory. Google those. Resistors and caps of all kinds are readily available and reasonably priced.
Logged

73 de Steve KE4OH
WB9TEN
Member

Posts: 10




Ignore
« Reply #10 on: March 26, 2019, 10:36:37 AM »

You didn't mention how your shop is equipped other than a lack of tub tester. I brought my SB-101 back to life with just a DVM for general troubleshooting but used a Heath IM-17 for the tuning. It is almost impossible to set to the "slow side of the peak" as part of the instructions direct with a digital meter.

Also, some of the tuning coils have two slugs. Make sure they aren't jammed together because that is a quick way to crack one.

I totally agree with the other advice. Have fun!

73
Dave
WB9TEN
Logged
K7MEM
Member

Posts: 724


WWW

Ignore
« Reply #11 on: March 26, 2019, 11:09:31 AM »

I won the bid a few days ago on a Heathkit SB-101 "technician special" -- seller says it powers up but has no output.  I don't yet have a power supply, so I won't be able to do anything with it when it arrives, but what kind of things can I expect to need fixing?  The photos don't show any obvious smoke marks or physical damage.

I would have been a little suspect of someone selling a SB-101 without a power supply. Especially when he says it powers up. How did he power it up?

But, I guess it's yours now. I see that there are SB-600s (matching speaker) with built in power supplies available on E-Bay. If you really want to deck it out, look for a SB-650. You will find them very hard to find.

I have a SB-101, with HP-23 power supply, and the SB-600 matching speaker. I also have a SB-650. It's been a while since I used it, so it probably needs some work. It's equipped with the 400 Hz CW filter. I also have a HP13 (12 volt power supply) so I can put the whole thing in my Yugo. Then I wouldn't have to use the heater. Smiley

Good luck with your SB-101.
Logged

Martin - K7MEM
http://www.k7mem.com
KX4QP
Member

Posts: 404




Ignore
« Reply #12 on: March 26, 2019, 03:27:46 PM »

I would have been a little suspect of someone selling a SB-101 without a power supply. Especially when he says it powers up. How did he power it up?

Same seller had an HP-23 (some version) with a taped-up connecting cord, opened minutes before or after the SB-101.  I presume that's how he powered it.  I had a bid on that, too, but it went out of my range (probably should have bid more, except I didn't have more money this month).  I saw 3-4 "HP-23 speaker power supply" (presumably the SB-600) last I looked, but they were in Canada and wanted CA$100 to ship them.  That's above $75 in real money.

I'll keep the HP-13 in mind as an alternative -- I could put a good sized gel cell battery and charger in the shack and be able to work for a short time with power out if needed (180W draw from an exit light battery ought to be good for an hour, more or less).  Of course, my luck the charger would put out enough RF noise to swamp the whole 40m band...
Logged
W5RKL
Member

Posts: 1113




Ignore
« Reply #13 on: March 26, 2019, 09:41:56 PM »

I have the complete SB-101 assembly manual on my website in pdf format.
Click the following link to download the manual.

http://w5rkl.com/wp-content/uploads/2014/04/SB101-complete-assembly-manual.pdf

There are a number of reason why the SB-101 has no RF output. The first test I would
perform is to check for 50ma idling current in either USB or LSB, it doesn't matter which
one. Set meter switch to PLATE, MIC/CW LEVEL control fully CCW, connect SB-101 to
a dummy load, and short pin 2 of the MIC socket. If the final tubes are conducting the
meter will rise to 50ma. The meter scales are shown on page 108 Figure 1-12 in the manual
(Adobe Reader page 124). The PLATE scale is 0, 100, 200, 300, 400 and 500. The 50ma
indication is the first small tick mark between 0 and 100 on the PLATE scale.

If the meter display 50ma or close to 50ma then the final tubes are conducting. If the
meter remains at zero then the tubes are not conducting which can be caused by one
or more of the following:

1. Both final tube filaments are OPEN (the final tube filaments are wired in "parallel")
2. Resistor R920 is OPEN (no final tube screen voltage)
3. Loss of HV which can result in excessive final tube screen current damaging the final
tube screens).
4. Problem with control relay RL2 terminals 3, 11, and 7 (RL2 pins 3, 11, and 7 control
switching the final tube screen voltage between receive and transmit).

RL2 pins 3, 11, and 7 change the final tube screen voltage as follows:
In receive the final tube screen voltage, pin 3, is approximately minus 4VDC turning the
final tubes OFF.

In transmit final tube screen voltage, pin 3, increases to approximately +235VDC turning
the final tubes ON.

The final tube screen voltage shown in manual "figure 1-13B Transmit Voltage Chart" shows
+235VDC is pointing to "pin 4" which is an error. Pin '3" of the 6146 is the screen. Pin 4 is the
Beam Forming element which is connected internally in the tube to the cathode pin 1.

There also could be other problems that contribute to loss of transmit RF output.

73
Mike W5RKL
www.w5rkl.com
RMC(SW) USN RET
Logged
KX4QP
Member

Posts: 404




Ignore
« Reply #14 on: March 27, 2019, 02:22:16 AM »

Thanks, Mike!  That kind of detail is the sort of thing I need.  I fix and troubleshoot stuff every day, for a living -- but the last time I fixed (tried to fix) something with tubes in it was around 1970-71, with the family TV.  A complex device like an SSB transceiver requires knowing where to look.

If it's an IR 2135 series impact wrench or a Hitachi NR83A family nail gun, I know exactly where to look, all the stuff that breaks or wears out, because I've fixed hundreds of them.  This will be my first radio repair, ever, unless you count replacing a fuse in some multi-band receiver my parents had when I was a kid.
Logged
Pages: [1] 2 3 4 5 6 ... 8 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!