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F5Turbo Illustrated Build Guide
F5Turbo Illustrated Build Guide
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Old 22nd February 2019, 03:18 PM   #481
elwood625 is offline elwood625  United States
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I'm interested in building the F5t mono blocks, however I have a couple of questions:
1 - The PC boards available from diy have provision for XLR connectors on the inputs, wiring the XLR's instead of RCA inputs, would this be a balanced input?
2 - The build shows Caddock resistors being used in R7 - R10, which according to the schematic would allow 110 ohms at 6 watts since there are two 220 resistors in series. What value Caddock was used? I only see 100, 120 and 150 values.
3 - Are the FET's and MOSFETS used in the build still available or am I late to the party?
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Old 22nd February 2019, 04:20 PM   #482
6L6 is offline 6L6  United States
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F5Turbo Illustrated Build Guide
1) The input would be balanced, yes.

2) Wherw are the big caddock available?

3) Still around, they go in and out of stock. Restock should be soon.
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Old 22nd February 2019, 05:38 PM   #483
Blitz is offline Blitz  Germany
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Ok, I exchanged in one channel the power mosfets... nope, stays cold.

Is there by any chance a schematic with voltages of individual check points available to figure out which part of my front end circuit died? By the way... is this ok to ask these questions here or should i go into the mammut builders thread?
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Old 22nd February 2019, 05:48 PM   #484
elwood625 is offline elwood625  United States
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Parts connection in Canada.


Caddock Resistors MP Series
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Old 22nd February 2019, 06:09 PM   #485
6L6 is offline 6L6  United States
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Blitz - this thread is fine.

Can you post a series of well-lit, in-focus photos so we can see what your current configuration looks like?
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Old 22nd February 2019, 06:12 PM   #486
6L6 is offline 6L6  United States
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Elwood - 120ohm will be fine.
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Old 22nd February 2019, 08:10 PM   #487
Blitz is offline Blitz  Germany
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Quote:
Originally Posted by 6L6 View Post
Blitz - this thread is fine.

Can you post a series of well-lit, in-focus photos so we can see what your current configuration looks like?
I can do this, no probs...but this will not help to find the issue as the amp looks now 100 percent idetical as it looked when it was working flawless...

There is simply a transistor or diode dead...and I need to figure out which one...currently it seems that the bias is too negative, so that no current is flowing, but for me its a bit unclear which voltgae should be where...The 25/35v rails ar there, but even with new output mosfet, not current flow...so...a bias thing I guess...
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Old 23rd February 2019, 02:08 AM   #488
6L6 is offline 6L6  United States
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Trying to see what configuration you have it in currently. No diodes? No thermistor? I understand the Diode Bridge as ground lift, but the other changes I need to see.
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Old 23rd February 2019, 05:40 AM   #489
nashbap is offline nashbap  United States
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Quote:
Originally Posted by elwood625 View Post
I'm interested in building the F5t mono blocks, however I have a couple of questions:
1 - The PC boards available from diy have provision for XLR connectors on the inputs, wiring the XLR's instead of RCA inputs, would this be a balanced input?

Are you referring to the diyaudio store F5T boards? If you want to go differential you will need two input boards and utilize the link on them.



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Old 23rd February 2019, 09:27 AM   #490
Blitz is offline Blitz  Germany
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6l6,

Thanks for looking into it.

The configuration is:
- Ground lift only with a 10ohm thermistor, no bridge this time.
- 25V 600Va transformer, only one, both channel on the same psu giving 36V without an amp as load and with both channels giving 32V (measured when the amp was working two years ago)
- Boards are the red v3 boards of the diyaudio store.
- Configuration: I have put the diodes and thermistors per output board back in. The diodes measure at 0,3V...I have measure other, new 3020w and those where 0,350V, not sure if this matters.
- Input configuration is cascode, so we have a classic F5Tv2 configuration in front of us.

I use a variac for power up, but there is no voltage to measure across the 0,5 ohm resistors I used (two mills 3w 1 ohm in parallel actually). As Voltage is there, power mosfets are new ones....I assume that the negative bias of the power mosfets is too negative to allow current flow, therefore my question which voltages should be seen in the front end pcb, I guess something died there...otherwise I will start to exchange all the transistors from the back to the front...
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