<div dir="ltr">Thank you, Chris, for the information. I have Heathkit SB-104A as the final amplifier. I nervously learned my HP-1144 power supply was designed without a crowbar circuit. I believe Heathkit realized and redesigned the HP-1144 to become HP-1144A. There is a company that provided piggyback PCB for the HP-1144 with a crowbar circuit. My power supply has a pair of large filter capacitors. It showed me that the terminals were not flat but looked like a "dome." I did not know if this was normal or not. I forced myself to get a switching power supply to take over.<br><br>I notice transceivers tend to lack a protection circuit for the final or power RF transistors as same with vacuum RF power tubes from overcurrent or overvoltage that are sure way to destroy it as same with heat. <br><br>My SB-104A has external cooling fans attached to the heatsink and also thermal sensors to watch out from overheating. Now, I am thinking about creating a new circuit to find a way to protect the RF transistors by restricting current and voltage. <br><div><br></div><div>Steven</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Sep 24, 2021 at 5:40 PM Chris Iwata <<a href="mailto:chrisiwata@aol.com">chrisiwata@aol.com</a>> wrote:<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>
<p><br>
</p>
<p>Well, we're off topic now. This thread was supposed to be about
the SB104 finals</p>
<p>To be fair, those MFC6030 ICs failed due to domino effect. <br>
</p>
<p>In both the SB104 and HP1144 regulator circuits, the IC current
capacity was boosted by a pass transistor. The transistor failed,
leading to failure of the IC. The transistor failed from
something connected to the regulator circuit drawing too much
current.</p>
<p>In the power supply case, this was dangerous. The transistor
shorted out. Instead of 13.8v going to the SB104, if there was no
crowbar, it would have been around 20v. <br>
</p>
<div>In the SB104 the voltage to the digital
ICs was too high, so they drew more current. It needed to be
4.75v to 5.25v. But because of 10% resistor tolerances it was
higher. So the transistor overheated. Luckily, in this instance
the transistor open circuited, so the regulator output voltage
went to zero. <br>
</div>
<div><br>
</div>
<div>Chris, KL7DM<br>
</div>
<div><br>
</div>
<div>On 9/22/2021 8:49 PM, Steven Feinsmith
wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div dir="ltr">Thank you, Chris, for clearing this up for me
about the MFC6030A voltage regulator by Motorola. Also, you
are correct that the HP-1144 power supply had no crowbar to
protect the transceiver included SB-634, SB-644A, and SB-614
through power chain links. The HP-1144A had an improved design
including a crowbar circuit.<br>
<br>
The price for MFC6030A went up crazy price at:<br>
<br>
<a href="https://store.americanmicrosemiconductor.com/mfc6030a.html" target="_blank">https://store.americanmicrosemiconductor.com/mfc6030a.html</a><br>
<br>
Fortunately, my HP-1144 is working except for my concern with
a pair of filter capacitors because the top terminals were not
flat. I do not know if it is normal because I did not have
another HP-1144 or HP-1144A for comparison. I plan to pull out
both filter capacitors to test for leakage and find their
capacitance range to ensure that they are ok or not. Secondly,
I plan a test ripple from them and use my infrared image gun
to see thermal reading for abnormal.<br>
<br>
Nowadays, it has become more difficult to buy large capacitors
because many companies are no longer in stock because of the
pandemic incidents. All vendors jacked up the price into
unreasonable costs for the replacement. That is why I got a
switching power supply designed for the Ham radio system to
replace the H-1144 in the SB-604 chassis. The advantage of the
switching power supply is that it is much lighter in weight
and smaller physically with a cooling fan. The device has
built-in overvoltage and overcurrent protection with
adjustable voltage and noise. The device is a TekPower TP30SWV
30 Amp DC 13.8V Digital Switching Power Supply with Noise
Offset.<br>
<br>
I know many Heathkit items need new parts replaced but are no
longer available. So many Heathkit items posted on eBay could
be around 90% not working while sellers want for hundred of
dollars and said, they applied the power and it on. That is
all. That was not correct how they tested the equipment before
selling it to buyers. Can we buy a non-working car at a price
that is supposed to be a working car? Of course, no! That
problem with sellers and eBay. Fortunately, I have experience
in electronics and can repair anything even if I have to
change the design to replace non-available components.<br>
<br>
It was not Heathkit's fault because they did not know what the
future would be. The problem is electronic component
manufacturers like Motorola, Texas Instruments, Emiac, and
many others enjoy discontinuing the products and allow many
people to cry and face jack up the prices as much as gold
prices.<br>
<br>
Thank you very much,<br>
Steven<br>
<div><br>
</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Wed, Sep 22, 2021 at
10:32 PM Chris Iwata <<a href="mailto:chrisiwata@aol.com" target="_blank">chrisiwata@aol.com</a>> wrote:<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>
<p><br>
</p>
<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>On 9/22/2021 4:51 PM, Steven Feinsmith wrote:<br>
</div>
<blockquote type="cite">
<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 align="RIGHT">Subject: </th>
<td>Re: [Heath] Fwd: Final transistors
for SB 104A</td>
</tr>
<tr>
<th valign="BASELINE" nowrap align="RIGHT">Date: </th>
<td>Wed, 22 Sep 2021 12:56:01 -0700</td>
</tr>
<tr>
<th valign="BASELINE" nowrap align="RIGHT">From: </th>
<td>Chris Iwata <a href="mailto:chrisiwata@aol.com" target="_blank"><chrisiwata@aol.com></a></td>
</tr>
<tr>
<th valign="BASELINE" nowrap align="RIGHT">To: </th>
<td><a href="mailto:ka9dzr@aol.com" target="_blank">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">heath@puck.nether.net</a><br>
To: <a href="mailto:heath@puck.nether.net" target="_blank">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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