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F6 Illustrated Build Guide
F6 Illustrated Build Guide
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Old 16th April 2016, 02:09 PM   #501
PJN is offline PJN  United States
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I opened My F6 up and replaced the burned R4 (18R) with a new one. Hooked up power and checked bias, was a bit high at ~ 0.6 V, then I noticed that R4 was very hot, lots of current going through so something else is bad. Looking at the schematic I'm taking a wild guess that Q1, or Q2 might have failed. All other components look good visually. I have a few spare IRFP240s in my spare parts so I'm going to replace both Q1 & Q2. Does anybody any other ideas ?

Paul
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Old 16th April 2016, 02:20 PM   #502
Zen Mod is online now Zen Mod  Serbia
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F6 Illustrated Build Guide
that means you had high output offset

recheck input JFets , just in case

that's easy - just measure voltage at their source's meet point , while IRFP outputs are out of circuit
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Old 16th April 2016, 02:37 PM   #503
oreo382 is offline oreo382  Canada
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Quote:
Originally Posted by Zen Mod View Post
that means you had high output offset

recheck input JFets , just in case

that's easy - just measure voltage at their source's meet point , while IRFP outputs are out of circuit
If output offset is that high then that means high across one of the Jfets?
That Jfet possibly cooked too?
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Old 16th April 2016, 02:45 PM   #504
Zen Mod is online now Zen Mod  Serbia
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well , I said - check JFets
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Old 16th April 2016, 03:20 PM   #505
PJN is offline PJN  United States
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Hi Zen Mod,

Before I saw your response I had already changed out Q1 & Q2, still same problem, R4 getting very hot, just blipped on the power briefly, I quess the Jfets are cooked like you suggested. At this point I think I'll just repopulate the entire board in case something else has been compromised. Is there a chance that the input transformers have been damaged ?

Thanks,

Paul
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Old 16th April 2016, 04:58 PM   #506
wdecho is offline wdecho  United States
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F6 Illustrated Build Guide
Doubtful but anything is possible. Not hard to check once you get them off the board. Just check continuity where it should be. You will probably have to destroy the board to get them off unless you are extremely good or lucky or both.
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Old 16th April 2016, 05:28 PM   #507
PJN is offline PJN  United States
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I'll just cross my fingers then and replace the rest, I can do that without destroying the board. Gotta go order some jfets.

Paul
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Old 16th April 2016, 11:39 PM   #508
Bare is offline Bare  Canada
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Small update on My F6 build.
Initially I wasn't happy with the sounds it produced... seemed as less than expected
Nothing wrong with my build or my speakers (checked everything to be sure)
Finally removed my George Wright penned tube/triode preamp..(which worked well in my preceeding setup).. fitted a 10 k Stepped atten cobble up as a rudimentary volume control ..a simple experiment.

INSTANT wonderful sounds.. a genuine Night And Day difference.
This one helluva good amp.
Sweet, Rich, exquisitely Detailed sounds.
Hearing is believing.

Matching seems as key and Good gear may not prove so good.. when the other bits are far better
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Old 17th April 2016, 04:35 AM   #509
Russellc is offline Russellc  United States
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F6 Illustrated Build Guide
Quote:
Originally Posted by Bare View Post
Small update on My F6 build.
Initially I wasn't happy with the sounds it produced... seemed as less than expected
Nothing wrong with my build or my speakers (checked everything to be sure)
Finally removed my George Wright penned tube/triode preamp..(which worked well in my preceeding setup).. fitted a 10 k Stepped atten cobble up as a rudimentary volume control ..a simple experiment.

INSTANT wonderful sounds.. a genuine Night And Day difference.
This one helluva good amp.
Sweet, Rich, exquisitely Detailed sounds.
Hearing is believing.

Matching seems as key and Good gear may not prove so good.. when the other bits are far better
Build yourself a BA3 front end as preamp, it compliments beautifully. Glad your amp is pleasing.

Russellc
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Old 17th April 2016, 12:52 PM   #510
Bones13 is offline Bones13  United States
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Some pre-amps have high output impedance that do not match well with these amps.
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