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Old 13th March 2009, 06:26 PM   #1
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Default Futterman H-3

Hey everybody,

I just picked up a Futterman H-3 stereo block which has been modified to use 4 x 6LF6's per channel. It originally had either 4 or 6 x 6FW5's per channel. The reason I say 4 or 6 of the FW5's is because the chassis has 6 holes punched per channel for the FW5's but I know Futterman was a then an now kind of guy so he may only have installed 4 per channel as the attached schematic shows. Also he used many different tube types for the H-3 although mine has the 6FW5 printed on each hole the attached schematic shows the 6HB5 as the output tube of choice.

Now the H-3 I picked up pretty much has the front end shown on the attached schematic. Once you get to the output tubes it starts to become a NYAL OTL3 which uses the 6LU8 as well as the SS TIP 50 for regulation.

In the end the workmenship on the wiring is terrible inside the amp. I mean a mess!!!!! The sockets suck and are ready to give up the ghost as well as several key parts. I touched a metal oxide 1 watt resistor in one of the reg circuits last night with a hemostat and it crumbled.

So a rebuild is what is up and coming. Starting like as soon as I make some choices and there is where I am looking for help from a few of the members here who have experience with this amp.

Should I go back to the 6FW5's or 6HB5's?
Should I stay with the 6LF6's?
What about 6 JJ Tesla EL509's per channel? Current wise that will match the 6FW5's since they have a max of 550mA and the JJ's are 500mA. 6 replaced by 6 does not cause me a transformer issue. The 6FW5's are octal as are the JJ's. Heater current is higher but I could take care of that with a small additinal trans I tuck inside the box as it is large and once the birds nest of wiring is fixed all will be good under the sun

Thought???

Thx in advance.
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File Type: gif original futterman h-3 reduced.gif (28.1 KB, 956 views)
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Old 13th March 2009, 06:27 PM   #2
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Here is the NYAL OTL3 Circuit
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File Type: pdf nyal otl3 reduced.pdf (54.8 KB, 296 views)
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Old 13th March 2009, 06:30 PM   #3
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Here is an H-3 with 4 x 6LF6's per channel. It is not mine but mine looks just like it.
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File Type: jpg futterman h-3 with 6lf6's reduced.jpg (27.3 KB, 796 views)
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Old 13th March 2009, 06:34 PM   #4
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Here is the 6FW5 data sheet.
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File Type: pdf 6fw5 data sheet.pdf (59.8 KB, 68 views)
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Old 13th March 2009, 06:42 PM   #5
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Here is an H-3 with 6 x 6FW5's per channel
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File Type: pdf 6fw5 futterman h-3 reduced.pdf (85.5 KB, 133 views)
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Old 13th March 2009, 06:55 PM   #6
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Here is Pg 1 of JJ EL509 data sheet
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Old 13th March 2009, 06:57 PM   #7
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Here is PG 2 of the JJ EL509 data sheet
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Old 13th March 2009, 07:04 PM   #8
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Here is an underside shot of a Futterman H-3 using either the 6HB5 or 6LF6 output tubes in a chassis with only 4 holes punched per side for outputs. We know this because it is a 12 pin socket so it has to be one of the two or maybe even some other 12 pin tube Julius liked.
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Old 13th March 2009, 09:35 PM   #9
adason is offline adason  United States
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Before you attempt any rebuild, you should read Harvey "Gizmo" Rosenberg's book "The search for musical ecstasy". Good one third of the book is about Futterman amp story.
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Old 13th March 2009, 09:37 PM   #10
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Quote:
Originally posted by adason
Before you attempt any rebuild, you should read Harvey "Gizmo" Rosenberg's book "The search for musical ecstasy". Good one third of the book is about Futterman amp story.

is it about the amp and how it was built, etc or is it his normal rambling?
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