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OLD GALAXY SATURN EPT360011B

I didn't look back to see how or what I wrote about taking
out the diodes, but I never had the idea that you met to physically
remove them! Thats really funny, seriously and respectfully!!!
It's all good !

Oh okay I see what I had typed...

What I met, are the devices that are piggy back on the finals, are these
what Nomadradio was talking about as far as these being the diodes.

I was saying this because I had never seen these type, especially attached
to the finals. And because I didn't see any other diodes around the finals, that was the reason I had asked if these are ones that you (Nomadradio) were talking about. Its funny how wording can be taking the wrong way! But I get it!

I just went back and read again what you had typed Nomadradio, and I didn't see
anywhere, where you typed "taking out" ! That was my wording not yours!!! Sorry for the mix up...
 
Last edited:
Cable Guy said:
I'd say so, I don't have the 11b schemo handy but the 14b schemo I have here, there are no additional diodes in the final pa section, and only one other, a 1n4148 diode, in the driver section called D90. I'd use the diode check on your DMM on the two MV1Y diodes (the ones attached to the transistors) for sure. Good luck!

View attachment 70123
Click to expand...
D89 is the diode across the driver D88 and D112 are the diodes across the finals.
plus_ept3600_11b_top_layout.gif
 
Somewhere along the line I have used the phrase "take out" to mean overloaded, blown, blasted, poofed or otherwise failed by an overload. Didn't even go back to see if I had said it that way.

There is a simple safety check you can perform to prevent new finals from getting poofed the first key.

After each transistor is bolted in place with a proper thin layer of heat-sink compound on both sides of the insulating washer, only solder the emitter (ground) and collector (center) leads. Leave the remaining lead standing straight up not connected. This is the transistor's base, or the input pin. Put the radio on sideband, won't matter which. Clip the meter's negative lead to the ground side of the big filter cap. Turn the mike gain to zero. Key the mike and probe the empty foil trace where the base terminal hasn't been soldered yet with the positive probe. Hold it keyed to make this measurement. You should see less that 7/10 of a Volt DC. Turning the bias trimpot for that transistor should reduce this to near zero, and turn up to not more than 7/10 of a Volt at the very maximum. Usually 7/10 or less. If you see more than that, it's time to find the failed part (or parts) in that bias circuit. If each final circuit passes this test, set each bias trimpot for zero Volts on the base pad of the circuit board for BOTH final transistors. Now (finally) solder the base lead of each final to the circuit board pad. This gives you a safe starting point to carefully turn up each bias trimpot safely to 60 mA on each final transistor.

Got tired of playing "final roulette" and adopted this protocol as a cost-reducing measure.

73
 
Last edited:
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999 said:
D89 is the diode across the driver D88 and D112 are the diodes across the finals.View attachment 70125
Click to expand...
Hello 999,
These diodes are mounted on what looks like a thin copper slab/plate.
The diodes themselves look like a glob of plastic almost like the shape of a half of a ball if you will.

Anyway, would you or anyone know where to purchase these? Or even
know what they are actually called? I can not imagine them being simply called a diode without another names of sorts attached to the word diode. They are not a typical axle type diode.

Thank you for attaching the the above schematics.
73
Rf Krazy
 
nomadradio said:
Somewhere along the line I have used the phrase "take out" to mean overloaded, blown, blasted, poofed or otherwise failed by an overload. Didn't even go back to see if I had said it that way.

There is a simple safety check you can perform to prevent new finals from getting poofed the first key.

After each transistor is bolted in place with a proper thin layer of heat-sink compound on both sides of the insulating washer, only solder the emitter (ground) and collector (center) leads. Leave the remaining lead standing straight up not connected. This is the transistor's base, or the input pin. Put the radio on sideband, won't matter which. Clip the meter's negative lead to the ground side of the big filter cap. Turn the mike gain to zero. Key the mike and probe the empty foil trace where the base terminal hasn't been soldered yet with the positive probe. Hold it keyed to make this measurement. You should see less that 7/10 of a Volt DC. Turning the bias trimpot for that transistor should reduce this to near zero, and turn up to not more than 7/10 of a Volt at the very maximum. Usually 7/10 or less. If you see more than that, it's time to find the failed part (or parts) in that bias circuit. If each final circuit passes this test, set each bias trimpot for zero Volts on the base pad of the circuit board for BOTH final transistors. Now (finally) solder the base lead of each final to the circuit board pad. This gives you a safe starting point to carefully turn up each bias trimpot safely to 60 mA on each final transistor.

Got tired of playing "final roulette" and adopted this protocol as a cost-reducing measure.

73
Click to expand...
Very interested Nomadradio, I like this concept.
You are always teaching us something, thank you.

73
Rf Krazy
 
The way they are mounted is meant to keep the diode at the same temperature as the heat sink next to the transistor. As a diode heats up the voltage drop across it will fall. The driver and final transistors have a similar quality. As they heat up this causes them to draw more current. The risk from this is called "runaway". The hotter the final gets the more current it draws. The more current it draws the hotter it gets. The bias diode serves to prevent this from becoming a downhill snowball effect. When the voltage across the bias diode falls, the voltage it allows to reach the transistor's input falls, turning down the transistor current and keeping it stable as it warms up.

A 1N4148 diode with the glass body against the plastic face of the transistor will serve more or less as well. A tiny dab of heat-sink compound will serve to conduct heat from the transistor to the diode.

The original part number was "MV1Y". Pretty sure it's obsolete, so only someone who has old stock will have them for sale.

73
 
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RF Krazy said:
Hello 999,
These diodes are mounted on what looks like a thin copper slab/plate.
The diodes themselves look like a glob of plastic almost like the shape of a half of a ball if you will.

Anyway, would you or anyone know where to purchase these? Or even
know what they are actually called? I can not imagine them being simply called a diode without another names of sorts attached to the word diode. They are not a typical axle type diode.

Thank you for attaching the the above schematics.
73
Rf Krazy
Click to expand...
Here is a paper from Texas Instruments on the diodes.

 
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nomadradio said:
Pretty sure that version used the Mitsubishi 2SC2312. It was discontinued almost 20 years ago. A chinese outfit called Hua Gao makes them now. Counterfeits appeared seemingly everywhere after the European Union's lead-free mandate prompted the end of its production. MOSFETs did not appear in this kind of radio until bipolars disappeared in the lead-free fiasco between 2006 and 2007.

These guys have the genuine "HG" copy.

https://www.icamanufacturing.com/shop/p/hg-2sc2312

They also have the HG copy of the nearly-identical 2SC1969. My advice is to read the numbers from the old parts and use that as a replacement.

When those fail, they tend to short inside and shoot the power-supply voltage from the collector circuit out the input terminal, the base. This toasts the bias diode, a 1-ohm resistor with a ferrite bead on one end and the bias trimpot. Simply dropping in a new final transistor will sometimes result in the new part being POOFED more or less right away. Once the base circuit and bias parts are known to be good it's safe to solder the leads on new finals.

The "-12" circuit board dates to around 30 years ago. Got replaced by the "14B" board in the mid-90s. The final section of the later 14B board is pretty much the same. Biggest differences are in the PLL section.

But that's been my experience, new bias trimpots, bias diodes and one fixed resistor on each final. Those trimpots will get 'dirty' or oxidized like a scratchy volume control. Good idea to replace them even if they weren't toasted in the breakdown.

73
Click to expand...
Nomadradio, I can't say enough about you! Seriously.

I ordered 10 of those 1969s. I remove the old and soldered in the new,
and they both worked just fine. Whats the bias, 3.5 amps? I think its 5 volts
for MOSFETs but being bipolar I think its about 3 to 3.5 amps on the bias. Is this correct? Man its been a while for me.

And those foil traces are terrible. I had to lay down two new traces on one of the finals. I was not happy, but the solder work that was done on this radio was just a mess. The frame has a lot of rust on it. And it looks like it had bugs in it at one time. Probably cock roaches, but I am not really sure. And I hope I didn't any with me when I brought the radio home. And then they're these fine hairs here and there. Where did these come from?

Well its back up and running! I was seeing about 30 watts before the finals
went out. Now it showing about 35 to 36 watts, maybe 37, on a slow peak watt meter made by Swan. (WM-3000)

Anyway Nomadradio, you need to be place in the Radio Hall of Fame. Again I am being serious !!!

I miss those CBTrick.com days. I never did hear what happen, if Benny had passed on or what? I still have his CDs that he used to mail out.

73
Rf Krazy
 
RF Krazy said:
Benny had passed on or what?
Click to expand...
Not to my knowledge. The CBT forum fell victim to a corrupted file with no backup. Efforts to reverse-engineer the immense pile of data and make sense of it never succeeded. Bennie lost interest in the main site, had changed jobs, kids getting older. Had plenty on his plate and too many demands on his time.

This naturally produced a flood of inquiries that just seemed to increase the shyness factor.

His ham call sign is still active, so I'll guess he's still above ground, at least. Haven't spoken to him in five years now, so my info is likely out of date.

73
 
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nomadradio said:
Not to my knowledge. The CBT forum fell victim to a corrupted file with no backup. Efforts to reverse-engineer the immense pile of data and make sense of it never succeeded. Bennie lost interest in the main site, had changed jobs, kids getting older. Had plenty on his plate and too many demands on his time.

This naturally produced a flood of inquiries that just seemed to increase the shyness factor.

His ham call sign is still active, so I'll guess he's still above ground, at least. Haven't spoken to him in five years now, so my info is likely out of date.

73
Click to expand...
Well thats better news on Bennie than what I had thought. Life in general can
certainly create new paths for us to go down, no matter if we plan for it or not.

Well I like to thank you Nomadradio for your valuable information and for your
willingness to share it. Over the many years you have always been there to help others along. Thank you.

And to 999, Xracerx13, and Cable Guy, I would like to thank you as well for sharing all that you had shared. Thank you.

73
RF Krazy
 

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