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Old 21st July 2010, 04:16 AM   #1
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Default Again with the HEX FREDs?

Yes, another HEX FRED thread.

This recent thread here says pretty much everything except the very thing I need to know.

The consensus is that this part number: Fairchild Stealth Diode ISL9R8120P2 is the replacement for the "FREDs" required on George's Simple SE board.

This is George's description of what a FRED is and where it goes on his board:

Click the image to open in full size.

"The photo shows the semiconductors used on this board. From left to right, constant current source IC's, Hex FREDs, and mounting hardware. Above them are the heat sinks required for the CCS IC's."

and also...

"...The heat sinks on the CCS IC's have the full B+ voltage on them DO NOT TOUCH THEM to see if they are hot when the amp is on! The tabs on the Hex FREDs are also carrying high voltage..."

OK here's what this tells me: The FREDs are not CCS ICs, and the CCS ICs are not FREDs.

Note: the photo above shows the CCS ICs to have three prongs, and the FREDs to have two.

The IXYS part that I bought (IXCP10M45S-ND) (for U10 and U20 on the Simple SE board) as per the parts list is going to blow sooner than later. I'd rather replace it now before I get it all together than after it's tucked away in it's chassis. This IXYS part in the parts list is a CCS IC (which I can only assume is different from the FREDs which--apparently--also blow).
People talk about the parts interchangeably I believe, but only ever mention a three prong replacement for the FREDs, and never a replacement part number--or even an original part number for that matter--for the two prong diode that goes into D1 and D2 (this is the part referred to as a FRED on the Simple SE manual). I still haven't ordered anything to go into this slot. The only thing my searching has turned up about this part (that intended for D1 and D2 referred to as a FRED) is the Fairchild three prong part.

Are they interchangeable? Is the Fairchild part recommended for both the FREDs and the CCS IC (U10 and U20)?

Do I simply snip the middle prong to insert the Fairchild part into D1 and D2?

Thanks for everyone's contributions to this rockin' board... (this forum and the Simple SE)

Here's my progress so far:

Click the image to open in full size.
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Old 21st July 2010, 07:51 AM   #2
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Ha ha, for two weeks I did nothing but research this diode. Of course, shortly after finally giving up and posting here I find this: clickity click

Apparently Mousers pictures are, indeed, 'for reference only'...

So, this part will go into D1 and D2. Do I need to replace my IXYS parts that I have in U10 and U20? (pn: IXCP10M45S-ND)

Thanks again,
randy
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Old 21st July 2010, 08:04 AM   #3
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I'll throw my 5 cents to this as I'm just about to order replacements for these myself.

Quote:
Originally Posted by stripe157 View Post
OK here's what this tells me: The FREDs are not CCS ICs, and the CCS ICs are not FREDs.
True. Two different things.

Quote:
Originally Posted by stripe157 View Post
Note: the photo above shows the CCS ICs to have three prongs, and the FREDs to have two.

...

People talk about the parts interchangeably I believe, but only ever mention a three prong replacement for the FREDs, and never a replacement part number--or even an original part number for that matter--for the two prong diode that goes into D1 and D2 (this is the part referred to as a FRED on the Simple SE manual). I still haven't ordered anything to go into this slot. The only thing my searching has turned up about this part (that intended for D1 and D2 referred to as a FRED) is the Fairchild three prong part.

Are they interchangeable? Is the Fairchild part recommended for both the FREDs and the CCS IC (U10 and U20)?
The Fairchild Stealth FRED you mention has only two prongs as it is a single configuration FRED (see http://www.fairchildsemi.com/ds/IS/ISL9R8120P2.pdf). Some FREDS have more prongs as there are FREDs commonly available in dual packages. From where did you get the impression that this part has three prongs ? I myself noticed at for atleast in Mouser's catalog this part has incorrectly a three prong thumbnail image which might mislead you. Please see the datasheet for exact specs for the part.

To answer your question these parts (U10 & U20 / D1 & D2) are not interchangeable and I think you should leave the CCS ICs as they are. I've yet to hear any problems with the CCS ICs (current regulators).

I'm not an expert with SimpleSE but I think you don't even need the D1 and D2 FREDs if you have a rectifier tube (as I think you do according to the picture you attached). AFAIK it's optional to use solid state rectifier or a tube rectifier with the thing.

BR,
Marko
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Old 21st July 2010, 06:31 PM   #4
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Thank you, that's exactly what I wanted to know. I did find the same datasheet you did that shows an accurate picture. Again, you are right, the thumbnail on Mouser's site is what mislead me.
What I still needed to know is whether to leave the CCS ICs in place or replace them now.
I will get the fairchild FREDs and solder them in now even if I don't use them yet. When it is time to try out different setups, I only want to plug in the switch, not pull the board out and solder on it again.
Thanks for the info,
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Old 22nd July 2010, 03:00 PM   #5
PDL is online now PDL  United States
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Leave the CCS alone, it will be just fine.
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Old 23rd July 2010, 06:16 AM   #6
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Thanks, I'll leave them alone then.
That's a bit of a relief, the board is pretty crowded now that everything else is on it.George really knew what he was doing when he put those instructions together.
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Old 13th August 2010, 04:29 PM   #7
Brit01 is offline Brit01  United Kingdom
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I just tried my old 1N4007's and it appears the freds listed below make quite a difference unless it's all in my imagination due to all the hype.

What are other users opinions between the 1N4007 and this Fred below?

HFA08TB60

Digi-Key - HFA08TB60-ND (Manufacturer - HFA08TB60)
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Old 13th December 2010, 11:22 PM   #8
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I'm in process of ordering parts.

So if I want to build a Simple SE with tube rectifier only then what other parts from this parts list are to be avoided along with D1, D2?

Parts Lists

Do I need CCS and heatsinks?


Last edited by imnewbie; 13th December 2010 at 11:35 PM.
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Old 13th December 2010, 11:46 PM   #9
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Quote:
Originally Posted by imnewbie View Post
So if I want to build a Simple SE with tube rectifier only...

Do I need CCS and heatsinks?
If you only want the tube rectifier, don't purchase the FRED (diodes) D1 and D2. If you install the optional filter choke, you won't need R1. You need all the other parts. You definitely need the CCS and heatsinks.
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Old 14th December 2010, 12:50 AM   #10
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Thanks Ty.
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