Greetings,
I was so intrigued by this project, I acquired all the bits. Being a little unsure of my SS DYI prowess and trying to live by the motto "DO no harm", i farmed this out to a friend from the AK forum who was happy to help. As fate fate would have it, my friend ended up getting to divorced, covid came, his father passed away and he moved from Philly to Virginia to help his mom. I eventually got back a mostly assembled but incomplete with issues unit. I'm hoping to trouble shoot what i have and bring it over the finish line with some help here. This is what i know.
PS tests good. When attached to amps, its blowing fuses.
As of now, i ordered fuses. I'm trying to find out how much testing (start up?) he attempted.
I'm sort of hoping he didn't follow the DBT variac procedure and it was just drawing too much current.
I reached out to Jim (6L6) and he suggested i bring project here and post photos of what i have right now. I can't do too much testing without fuses which i expect later this week. In the meantime here are some photos of the work in process that i have.
Oh and thanks in advance for the support Andy
I was so intrigued by this project, I acquired all the bits. Being a little unsure of my SS DYI prowess and trying to live by the motto "DO no harm", i farmed this out to a friend from the AK forum who was happy to help. As fate fate would have it, my friend ended up getting to divorced, covid came, his father passed away and he moved from Philly to Virginia to help his mom. I eventually got back a mostly assembled but incomplete with issues unit. I'm hoping to trouble shoot what i have and bring it over the finish line with some help here. This is what i know.
PS tests good. When attached to amps, its blowing fuses.
As of now, i ordered fuses. I'm trying to find out how much testing (start up?) he attempted.
I'm sort of hoping he didn't follow the DBT variac procedure and it was just drawing too much current.
I reached out to Jim (6L6) and he suggested i bring project here and post photos of what i have right now. I can't do too much testing without fuses which i expect later this week. In the meantime here are some photos of the work in process that i have.
Oh and thanks in advance for the support Andy
to Phoenix NJ
Hello Phoenix NJ,
I also answered in the F5-Turbo-builders-thread:
You seem to have a F5T V2. You have one pair of JFets and no cascodes on the frontendboard.
Please measure your railvoltages (I assume you have around +-32V)?
You should get a dim-bulb-tester for first start-up....
Check pic below with instructions of 6L6 and some additions from me.
Greets
Dirk
Hello Phoenix NJ,
I also answered in the F5-Turbo-builders-thread:
You seem to have a F5T V2. You have one pair of JFets and no cascodes on the frontendboard.
Please measure your railvoltages (I assume you have around +-32V)?
You should get a dim-bulb-tester for first start-up....
Check pic below with instructions of 6L6 and some additions from me.
Greets
Dirk
Attachments
to Phoenix NJ #1106
Hello Phoenix NJ,
the cascode is optional up to railvoltage around +-33-34V (the Toshibas and
Linear Systems can withstand this - they will not survive 40 v and more).
My F5T-Monoblocks are running on railvoltages of +-42,8 V. And I have more Mosfets in the outputstage. So it was strictly necessary to use cascode BJTs and
2 pairs of JFets per channel. You don't need it.
Cheers
Dirk
Hello Phoenix NJ,
the cascode is optional up to railvoltage around +-33-34V (the Toshibas and
Linear Systems can withstand this - they will not survive 40 v and more).
My F5T-Monoblocks are running on railvoltages of +-42,8 V. And I have more Mosfets in the outputstage. So it was strictly necessary to use cascode BJTs and
2 pairs of JFets per channel. You don't need it.
Cheers
Dirk
No, I'd suggest that you measure across R5 and R6 as Dennis suggested.
Edited to add just in case it's not clear. With no power to the amplifier; place your DMM probes on either side of R5 (then R6); set your DMM to resistance; turn P1 (P2) until your DMM reads the lowest resistance. It should be below an ohm or two. If it's not, post back.
Check schematic to note that R5 and R6 are in parallel with P1 and P2 to understand Dennis' suggestion a bit further.
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My 2 cents:
1 - Go to FIRSTWATT.com and read the article for the F5 Turbo, then read it again. I read it every night while I was building mine.
2 - Move the thermistor away from the metal mounting bolt for the MOSFET, it must touch the plastic case of the MOSFET. They are known to short to ground and cause sparks, smoke and flames. Not good.
3 - GO SLOW, this amp will bite even the best amp builders.
4 - Take your time adjusting the bias, 1/4 turn of P1 and then a 1/4 turn for P2. Remember which one is CW to increase and which is CCW to increase, I marked mine with drop of red (P channel) and white (N channel) paint.
5 - Don't go above 300mV on the bias adjust, let it cook for a week before you attempt to go above 300mV.
6- Buy a small fire extinguisher and keep it close by, I have two, one for each side of the bench.
7- Build and use a dim bulb tester, it has saved me more times than I care to admit.
1 - Go to FIRSTWATT.com and read the article for the F5 Turbo, then read it again. I read it every night while I was building mine.
2 - Move the thermistor away from the metal mounting bolt for the MOSFET, it must touch the plastic case of the MOSFET. They are known to short to ground and cause sparks, smoke and flames. Not good.
3 - GO SLOW, this amp will bite even the best amp builders.
4 - Take your time adjusting the bias, 1/4 turn of P1 and then a 1/4 turn for P2. Remember which one is CW to increase and which is CCW to increase, I marked mine with drop of red (P channel) and white (N channel) paint.
5 - Don't go above 300mV on the bias adjust, let it cook for a week before you attempt to go above 300mV.
6- Buy a small fire extinguisher and keep it close by, I have two, one for each side of the bench.
7- Build and use a dim bulb tester, it has saved me more times than I care to admit.
Measuring across R5 and R6 (1K) They were set very high. I dialed them both down to a couple of ohms on both boards. Hopefully that was the issue. Fuses will be here in a day or 3. once i have. I'll hook up through variac and DBT and see what's up. I'm cautiously optimistic at this point Thanks for the guidance again.
I appreciate input.
Truthfully I read it several times before I decided to hand it off.
I read it again twice since I got it back and have been rereading sections as I come to things I haven't completely wrapped my head around . This is my first SS build. I've done a bunch of tube rebuilds and a couple of builds . Some kits and some from scratched following well worn paths. I'm not looking to blaze new ground here ( literally or figuratively).
I have a fire extinguisher but hadn't thought to have it by the bench. I'll have to rectify that.
I'll look into moving the thermistor as well . I've done a little house keeping inside this since I started thread. I'll have to address that.
Truthfully I read it several times before I decided to hand it off.
I read it again twice since I got it back and have been rereading sections as I come to things I haven't completely wrapped my head around . This is my first SS build. I've done a bunch of tube rebuilds and a couple of builds . Some kits and some from scratched following well worn paths. I'm not looking to blaze new ground here ( literally or figuratively).
I have a fire extinguisher but hadn't thought to have it by the bench. I'll have to rectify that.
I'll look into moving the thermistor as well . I've done a little house keeping inside this since I started thread. I'll have to address that.
Yes, about a quarter of the way through the thread, it was discovered by a builder who had the thermistor against the washer. The red on the tip of the thermistor is paint, and not very thick, the heat from the MOSFETs may harden the paint so it chips and then shorts out. What ever the cause, it was not a pleasant outcome.
What model Antek transformer is being used? What value(s) / type of fuses did you get?
While we wait, do mind if I pick the collective minds on the ground lift circuit?
I see in
Post #40 F5 turbo builders thread.
The F5 PS drawing and the F5T PS drawing slight differences in the way they inserted the Current limiters ( also the use of a CL-30 in the F5T.
F5 TURBO Illustrated build guide post #1 power supply images
In this build I see using 2 CL-60s to isolate(?) The two primary windings like in the original F5 ps drawing I mentioned.
Is there any right ( better ?) Way of doing this?
I suspect little difference to be found. It just makes me pause when I see it implemented in different ways.
I see in
Post #40 F5 turbo builders thread.
The F5 PS drawing and the F5T PS drawing slight differences in the way they inserted the Current limiters ( also the use of a CL-30 in the F5T.
F5 TURBO Illustrated build guide post #1 power supply images
In this build I see using 2 CL-60s to isolate(?) The two primary windings like in the original F5 ps drawing I mentioned.
Is there any right ( better ?) Way of doing this?
I suspect little difference to be found. It just makes me pause when I see it implemented in different ways.