[Heath] Fwd: Fwd: Final transistors for SB 104A

Wed Sep 22 22:32:33 EDT 2021

When I mentioned restoring the SB104 that meant bringing it back to as 
originally sold.  No workarounds.

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.

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.

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.

Chris, KL7DM

On 9/22/2021 4:51 PM, Steven Feinsmith wrote:
> 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.
>
> The same problem with SB-230 uses a 1KW tube that was no longer stock 
> and depleted from the vendor's inventory.
> Some Ham users use Russian-made microwave tubes to take over with some 
> modifications.
> 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.
>
> Now, I am working on a new PCB for the SB-104A display to run with the 
> LED instead of Panaplex.
>
> 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.
>
>
> 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.
>
> Just try to keep Heathkit alive ahead of time!
> Steven
>
>
>     -------- Forwarded Message --------
>     Subject: 	Re: [Heath] Fwd: Final transistors for SB 104A
>     Date: 	Wed, 22 Sep 2021 12:56:01 -0700
>     From: 	Chris Iwata <chrisiwata at aol.com> <mailto:chrisiwata at aol.com>
>     To: 	ka9dzr at aol.com <mailto:ka9dzr at aol.com>
>
>
>
>
>     If you luck out and find some,  bear in mind that you have to buy
>     matched pairs.
>
>     Theoretically, you have to buy matched quads.  But you can
>     probably be OK with matched pairs
>
>     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
>
>     Your best bet is to buy a junked SB104
>
>     The SB104 will become unrestorable due to unavailability of the
>     Final transistors, the Nixie tubes, the Nixie driver IC, and the
>     voltage regulator IC.
>
>     Chris, KL7DM
>
>
>
>     On 9/22/2021 10:18 AM, ka9dzr--- via Heath wrote:
>>     has anyone fine any replacement finals for the sb-104a yet  tnx
>>     ka9dzr Dennis
>>
>>         ------------------------------------------------------------------------
>>         From: heath at puck.nether.net <mailto:heath at puck.nether.net>
>>         To: heath at puck.nether.net <mailto:heath at puck.nether.net>
>>         Sent: 11/24/2014 4:56:23 PM Central Standard Time
>>         Subject: [Heath] Final transistors for SB 104A
>>
>>         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.
>>         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
>>         _______________________________________________
>>         Heath mailing list
>>         Heath at puck.nether.net <mailto:Heath at puck.nether.net>
>>         https://puck.nether.net/mailman/listinfo/heath
>>         <https://puck.nether.net/mailman/listinfo/heath>
>>
>>
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