Fw: Query: HW-104 boards vs SB-104A boards + need rear-wall power plug

[Kees & Sandy]

Hi Jim, there are at least two SB-104A repair sites. One is mine
which you can get to via  http://www.qsl.net/k5bcq/  The other
one is Mike Bryce's. As to your specific question, you can swap
out all the boards. There is a difference between the "G" boards.
The earlier HW-104/SB104 boards (with several FETs) have an
RF gain input on pin 5 and the later "G" boards (one RF transistor)
have this point grounded. Not a problem as long as you have a
series resistor to +11V on the second RF gain control. The rest
of the cards have the same pin-outs .....HOWEVER, these units
often tend to be modified/improved.

The later boards will have more fixes, updates, and changes
installed on them and I would advise fixing them.

One of the first things to go are the small 6 pin regulators in both
units. Some people on the reflector have spares and will probably
contact you. Missing fuses and fuse caps on your PS is not a good
sign. Reversing the +12V to this unit will take out hardware, VERY
quickly (so will overvoltage), so be careful if the plug is bad. The
11-pin plug is available commercially today......for example
(maybe less $$ elsewhere):

Newark Catalog 119 2001-02
11 pin plug       WPI p/n 86-cp11   $4.14
cap w/t clamp WPI p/n 86-3-858  $6.43
11 pin skt.       WPI p/n 78-S11     $5.45
Mike Connector
Male Plug       WPI p/n 80MC2M $11.99

By the way..........
The often heard problem of 104s is that the output transistors are
"very sensitive" and go out ....is not really true. I've had them up
to 170W (for a short duration) with the ALC removed. Just follow
the tuning procedures in the manual and you should have no
problems. Most "low output" problems are something else and the
output transistors are really pretty hearty. Not so for the 6 pin
voltage regulators.

73s  Kees K5BCQ


----- Original Message -----
From: Jim Larsen <AL7FS at ARRL.NET>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Friday, November 02, 2001 5:00 AM
Subject: Query: HW-104 boards vs SB-104A boards + need rear-wall power plug


> Greetings from Alaska,
>
> I have a sick SB-104A and sick 1144 PS.  Both appear to be out of
> service.  I am using an Astron SS-25 with a Heath power cord made up to
> begin troubleshooting the SB-104A.  It failed the very first B board and
> readout check.  :-(
>
> Here is my question and my hope:
>
> I have what appears to be a complete set of boards for an HW-104 or
> 104A.  The numbers do not match those in my SB-104A.  I notice that the
> board colors are different.  The SB boards are a green color and the
> other set a beige color.
>
> My question:  Can someone tell me which, if any, of the HW boards will
> work in the SB-104A?  Perhaps a cross-reference listing of board numbers
> or by function name that are interchangeable?  I have the manuals for
> the SB-104A but of course have none for the HW-104(A).  I can eyeball
> the boards but that is no substitute for already existing knowledge.
>
> My hope:  The power plug on the back of the SB-104A has the center pin
> broken out.  Does anyone have a replacement 11 pin mail plug I can
> install in the back wall of the radio?  The power cord has the female 11
> pin.  Let me know cost and shipping if you have one you can spare.
> Also, both of the fuse holder tops and fuse are missing from my 1144
> PS.  Anyone have some old tops that will fit so I can put fuses back in?
>
> Wish me luck.  My troubleshooting skills are NOT legendary.   :-)
>
> Thank you.
>
> 73, Jim
> --
> Jim Larsen,  AL7FS,  Anchorage, Alaska
> (BP51cc) - 61.101 North, 149.824 West
> mailto:al7fs at arrl.net - http://www.qsl.net/al7fs/
>
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