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Author Topic: Unknown electronic symbol  (Read 1183 times)
K8AXW
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« on: July 06, 2019, 02:26:13 PM »

I have a schematic for an older Pyramid 13.8VDC power supply that uses a symbol that I have never seen in 63 years of hamming. 

I don't have the power supply to look at....just the schematic.

Since I can't draw the symbol here or provide a photo of the symbol I'll try to describe it:

Picture a straight line between two components and in the middle of this line or wire is a FLAT BOTTOMED "U" ( or this might be closer  "]" and labeled F1 through as many as in the power supply...which is at least F30.  I THINK they represent ferrite beads but I'm guessing. Considering where they're located also males me think "ferrite bead." I'm familiar with the FB1 through....whatever which represents "Ferrite bead."

Anyone have an idea of what this might be from my poor description?

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K3GM
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« Reply #1 on: July 06, 2019, 02:59:54 PM »

Sounds like you might be describing a thermal fuse symbol.
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AC2EU
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« Reply #2 on: July 06, 2019, 03:18:16 PM »

Sounds like you might be describing a thermal fuse symbol.

Good guess, but I don't there are 30 fuses in there.
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K4SAV
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« Reply #3 on: July 06, 2019, 04:14:51 PM »

Do you mean something like this?
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WB0DZX
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« Reply #4 on: July 06, 2019, 10:26:23 PM »

May we have the model number of the power supply associated with the schematic in question?
 
Mike WBØDZX
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WW7KE
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« Reply #5 on: July 06, 2019, 10:33:42 PM »

Do you mean something like this?


Obviously that's a symbol for an electrolytic capacitor, the "bracket" symbol being the negative.  I don't think it's used much anymore in the US.  Europe, maybe?
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K8AXW
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« Reply #6 on: July 06, 2019, 10:56:49 PM »

SAV: 

Close but no cigar! The symbol you provided in your answer is exactly like  what I'm trying to describe EXCEPT the end of the lead coming in from the left, going into the "cup" does NOT have a heavy bar at the end. The lead does not touch the bottom of the cup. The lead from the right in your drawing does touch the "cup" bottom just as you have drawn it. It definitely isn't an electrolytic.

It is not a capacitor because for example there are 2 on the + lead of the ammeter and one on the negative lead from the ammeter; there is one on each pass transistor base lead. Looks like around 30 of them scattered around the power supply which to answer DZX is a Pyramid PS-35G.

Each one of these symbols are labeled F1, F2, F3 etc.
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WW7KE
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« Reply #7 on: July 06, 2019, 11:04:47 PM »

SAV: 

Close but no cigar! The symbol you provided in your answer is exactly like  what I'm trying to describe EXCEPT the end of the lead coming in from the left, going into the "cup" does NOT have a heavy bar at the end. The lead does not touch the bottom of the cup. The lead from the right in your drawing does touch the "cup" bottom just as you have drawn it. It definitely isn't an electrolytic.

It is not a capacitor because for example there are 2 on the + lead of the ammeter and one on the negative lead from the ammeter; there is one on each pass transistor base lead. Looks like around 30 of them scattered around the power supply which to answer DZX is a Pyramid PS-35G.

Each one of these symbols are labeled F1, F2, F3 etc.

F is usually used for fuses, but that doesn't make sense with your description.  It almost sounds like you're describing an FET, but you don't say there's an arrow on the single lead, which would be the gate.

If you could find a way to scan the schematic and post it here, or try to duplicate some of it with a graphics program, that would be a big help.
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K4SAV
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« Reply #8 on: July 07, 2019, 05:31:53 AM »

Old schematic of PS-35A power supply using the symbols described.
http://www.repeater-builder.com/pyramid/pdfs/PS35GY.pdf

Those are obviously connector symbols, although I have never seen a connector symbol exactly like that before either.  Probably something similar to the little plastic connectors you see on a lot of circuit boards.

Schematic of PS-35A without the connector symbols.
http://www.repeater-builder.com/pyramid/pdfs/PS35GN.pdf

Jerry, K4SAV
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W9IQ
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« Reply #9 on: July 07, 2019, 05:55:28 AM »

It could be that the "F" circuit designator is for Faston style connectors.



- Glenn W9IQ
« Last Edit: July 07, 2019, 06:00:23 AM by W9IQ » Logged

- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
W6EM
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« Reply #10 on: July 07, 2019, 06:40:23 AM »

Old schematic of PS-35A power supply using the symbols described.
http://www.repeater-builder.com/pyramid/pdfs/PS35GY.pdf

Those are obviously connector symbols, although I have never seen a connector symbol exactly like that before either.  Probably something similar to the little plastic connectors you see on a lot of circuit boards.

Schematic of PS-35A without the connector symbols.
http://www.repeater-builder.com/pyramid/pdfs/PS35GN.pdf

Jerry, K4SAV

Also, worthy of note here is that there are NO emitter ballast resistors in the PS-35, or any other Pyramids that I've salvaged.  Most of them end up failing one or more pass transistors for just that reason.  Whereas Astron and others who use paralleled power transistors use the emitter resistors to compensate for unequal gains and "current hogging" by the highest gain transistors and eventual overcurrent failure(s).  The first thing I do is add low value ballast resistors to fix their design.....  And, then they'll behave like they should.
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K8AXW
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« Reply #11 on: July 07, 2019, 10:19:04 AM »

Glenn, I'm inclined to agree with you but I need to see this power supply and have a look.  I sold it to a guy for him to repair without even looking inside.

EM:  You're absolutely correct on the emitter resistors.  I have a PS-26XK and it has no emitter resistors as the Astrons do. HOWEVER  the Pyramids have resistors in the BASE lead and the Astrons do not. 

Would this in effect serve the same purpose?

At any rate my Pyramid will get emitter resistors as repairs get going.
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WW7KE
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« Reply #12 on: July 07, 2019, 11:01:14 AM »

It could be that the "F" circuit designator is for Faston style connectors.

It definitely is.  Per the schematic, those points are where the chassis-mounted parts (pass transistors, meter, etc.) connect to the circuit board.  The "stub" part of the symbol is the PWB-mounted Faston clip, and the "bracket" part is the spade lug with the wire that connects to the chassis part.

That's a logical way of drawing such a connection symbol, but I've never seen them drawn that way.
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WB0DZX
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« Reply #13 on: July 07, 2019, 03:45:04 PM »

The latter posts are correct. Found one blurry pic at https://www.worldwidedx.com/attachments/136-jpg.3963/

But the F designation could still mean "fuse" if there is a catastrophic failure vaporizing the interconnect wire(s).
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W6EM
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« Reply #14 on: July 08, 2019, 07:17:35 PM »

...........
EM:  You're absolutely correct on the emitter resistors.  I have a PS-26XK and it has no emitter resistors as the Astrons do. HOWEVER  the Pyramids have resistors in the BASE lead and the Astrons do not. 

Would this in effect serve the same purpose?

At any rate my Pyramid will get emitter resistors as repairs get going.
Sorry to be late in responding, but we were travelling.  Similar, but not quite.  Think about the emitter resistor developing enough reverse bias to completely turn off the particular transistor.  A series resistor in the base circuit would tend to lower the driving base voltage for high base input currents.  That also would lower the emitter voltage.  Some reduction, but not as much.  At least I think not.  I could be wrong.  Also, Pyramid doesn't have a reverse-biased diode across the collector-emitter junction of the output transistors.  Useful to avoid transient damage.

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