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<p>When I mentioned restoring the SB104 that meant bringing it back
to as originally sold. No workarounds.</p>
<p>The MFC6030 voltage regulator IC in the SB104 is the same as in
the HP1144 power supply. On my SB104 it failed, and the one in the
power supply also failed. This is a 4 terminal regulator no
longer in production and only Motorola made it. I couldn't even
find an NTE replacement. ICs theoretically last almost forever,
but practically they don't. Ultimately I used a 7805K for the
SB104 and completely redid the power supply using a LM723
regulator.</p>
<p>The computer grade cap in the power supply used to be cheap as
surplus when computers used TTL ICs. but no more. The one in my
power supply failed also. The 1144 power supply I own had no
crowbar overvoltage protection, I added it myself. This was added
in 1144A version. This is very important if you want to protect
your SB104 from disastrous failure. <br>
</p>
<p>One final RF transistor blew. This happened from high VSWR.
Rather than buying a matched pair or quad, I redid the final to
use only 2 transistors at reduced wattage. <br>
</p>
<p>Chris, KL7DM<br>
</p>
<div class="moz-cite-prefix">On 9/22/2021 4:51 PM, Steven Feinsmith
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAGJMgmVJhkj9Ob6k8b_AiLndjxg+NjkqVTY9WDFoz+MiCPKx7w@mail.gmail.com">
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<div dir="ltr">
<div class="gmail_quote">
<div>First of all, both SB-104, SB-104A, and SB-230 are not
dying. The 2N6456 RF transistors have indeed become more
difficult to find nowadays. The greedy eBay sellers pumped
for around 100 dollars each. Of course, no one is buying 400
dollars. There is a big issue about whether a matched quads
may be impossible. I did mention in my previous message that
I should buy an old rig that uses the 2N6456.<br>
</div>
<div><br>
</div>
<div>The same problem with SB-230 uses a 1KW tube that was no
longer stock and depleted from the vendor's inventory.<br>
Some Ham users use Russian-made microwave tubes to take over
with some modifications.<br>
</div>
<div> </div>
<div>The front panels use a Panaplex display. It is a gas
discharge display that was very popular and easy to read.
There was a slight problem with the Panaplex because it
requires 180 volts to run the gas discharge. It tended to
give out some electrical noise. There are articles about
converting Panaplex to LED for both SB-634, station, and
SB-104A, transceiver.<br>
</div>
<div><br>
</div>
<div>Now, I am working on a new PCB for the SB-104A display to
run with the LED instead of Panaplex.<br>
</div>
<div><br>
</div>
<div>The problem is with the new ham radio transceivers that
physically shrink a lot, but it had many features, such as
digital modes with USB ports. The amplifier tends to use
high-power transmitting tubes now as MOSFET. The price tag,
OUCH! I am poor as a retiree and earn a social security
retirement check every month.<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div>
<div><br>
</div>
</div>
</blockquote>
<div>You mentioned voltage regulators. My SB-104A is running
fine as a licensed operation tested them. I checked
everything with my DMM/VTVM to ensure voltages are within
specification. Can you explain the details about the voltage
regulators. I also found my HP-1144 power supply seems to
have two filter capacitors that may need replacement. The
cost is crazy as I bought a switching power supply that
provides matched voltage and provides 30A instead of 20A
with overvoltage and overcurrent protection. The advantage
with the switching power supply was that it was very light
compared with a massive transformer's weight.</div>
<div><br>
</div>
<div>Just try to keep Heathkit alive ahead of time!</div>
<div>Steven</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div>
<div><br>
-------- Forwarded Message --------
<table cellspacing="0" cellpadding="0" border="0">
<tbody>
<tr>
<th valign="BASELINE" nowrap="nowrap"
align="RIGHT">Subject: </th>
<td>Re: [Heath] Fwd: Final transistors for SB 104A</td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap"
align="RIGHT">Date: </th>
<td>Wed, 22 Sep 2021 12:56:01 -0700</td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap"
align="RIGHT">From: </th>
<td>Chris Iwata <a
href="mailto:chrisiwata@aol.com"
target="_blank" moz-do-not-send="true"><chrisiwata@aol.com></a></td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap"
align="RIGHT">To: </th>
<td><a href="mailto:ka9dzr@aol.com"
target="_blank" moz-do-not-send="true">ka9dzr@aol.com</a></td>
</tr>
</tbody>
</table>
<br>
<br>
<p><br>
</p>
<p>If you luck out and find some, bear in mind that you
have to buy matched pairs.</p>
<p>Theoretically, you have to buy matched quads. But
you can probably be OK with matched pairs</p>
<p>Expect to pay a premium, those stud mount RF
transistors haven't been made for at least 20 years. A
guess would be at least $50 each<br>
</p>
<p>Your best bet is to buy a junked SB104</p>
<p>The SB104 will become unrestorable due to
unavailability of the Final transistors, the Nixie
tubes, the Nixie driver IC, and the voltage regulator
IC. <br>
</p>
<p>Chris, KL7DM</p>
<p><br>
</p>
<p><br>
</p>
<div>On 9/22/2021 10:18 AM, ka9dzr--- via Heath wrote:<br>
</div>
<blockquote type="cite">
<div>
<div
style="font-family:arial,helvetica,sans-serif;font-size:10pt;color:rgb(0,0,0)">
<div><span
style="font-family:arial,helvetica,sans-serif;font-size:10pt;color:rgb(0,0,0)"> </span></div>
<div><span
style="font-family:arial,helvetica,sans-serif;font-size:10pt;color:rgb(0,0,0)">has
anyone fine any replacement finals for the
sb-104a yet tnx ka9dzr Dennis</span></div>
<div> </div>
</div>
<div>
<blockquote
style="padding-left:5px;margin-left:5px;border-left:2px
solid blue">
<hr><span
style="background-color:transparent;color:rgb(0,0,0);font-family:Arial;font-size:small"><span
style="background-color:transparent;color:rgb(0,0,0);font-family:Arial;font-size:small">From:
<a href="mailto:heath@puck.nether.net"
target="_blank" moz-do-not-send="true">heath@puck.nether.net</a><br>
To: <a href="mailto:heath@puck.nether.net"
target="_blank" moz-do-not-send="true">heath@puck.nether.net</a><br>
Sent: 11/24/2014 4:56:23 PM Central Standard
Time<br>
Subject: [Heath] Final transistors for SB
104A<br>
<br>
</span></span>
<div dir="ltr">I have learned that the 2n6456
final RF transistors are no longer available
and I NEED to replace the four (4) in a Heath
SB 104A. Has anyone found a suitable
replacement transistor for this application? I
have thoroughly checked with RF Parts and they
no longer stock those transistors.</div>
<div dir="ltr"> </div>
<div dir="ltr">Does anyone have experience
substituting the final transistors in the SB
104A? If so what did you use as a replacement
and do you know where they can be found?
Thanks and 73, John, K5PGW</div>
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