F5Turbo Illustrated Build Guide

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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?
 
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?
 
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...
 
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.



nash
 
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...
 
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...


What is the voltage across R5? Does it change when you turn P1? If turning P1 to its max results in no significant increase in voltage then P1 has likely gone bad.

What about the P2 side voltages?


nash
 
So in order to build two mono block balanced amps, I would build two stereo amps with the input boards linked using a single XLR input for each amp. Would the outputs boards for each amp be out positive and the other out negative?


For each balanced monoblock you will have two input boards. Lets say for the Left channel monoblock, L signal + will go to one input board and L signal- will go to the other input board. The output boards connected to the one input board will generate an output signal , likewise the other input/output combo. These two outputs are connected to your speaker. There is no ground wire to the speaker.
Hope this helps. nash
 
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Is there enough room on the back panel of the 5U deluxe chassis to mount:
1 XLR connector
1 pair of speakers connectors
IEC connector
2 FE boards?
I would like to mount both FE boards on the rear panel to keep the "link" wire for XLR balanced operation short along with the input wires.
I understand AndrewT's concerns about mains wiring, I was planning on having the transformer mid way on the bottom panel and the PSU board near the front panel. This way I can mount the soft start PC board close to the rear panel.