Is anyone building the DIY Pass F-5

strider · « **Reply #60 on:** 23 Feb 2011, 03:06 pm »

Russell,

Did you use 4-40 bolts to attach the JFETs to the heatsinks? Do you recall how long they were? What are you using to insulate the JFEts from the heatsinks?

I've got a pile of F5 parts scattered about my house. The case and especially dealing with the heatsinks have been the most imposing thing for me.

avionic · « **Reply #61 on:** 23 Feb 2011, 04:11 pm »

Ordered IRF's. I do find myself looking at a matched set of toshiba's for quite a bit more $$. Heat sinks will be conrad. The rest is still up in the air. I like to do as much reading/research before I make a decision.

Russellc · « **Reply #62 on:** 23 Feb 2011, 07:23 pm »

Quote from: strider on 23 Feb 2011, 03:06 pm

Russell,

Did you use 4-40 bolts to attach the JFETs to the heatsinks? Do you recall how long they were? What are you using to insulate the JFEts from the heatsinks?

I've got a pile of F5 parts scattered about my house. The case and especially dealing with the heatsinks have been the most imposing thing for me.

I used sil pads on my build. I have since aquired mica, which supposed to be superior, but now I have been shown Zhou's Kerafol or what ever, and they are supposed to be superior to that....we'll see.

Russellc

Russellc · « **Reply #63 on:** 23 Feb 2011, 07:25 pm »

Quote from: strider on 23 Feb 2011, 03:06 pm

Russell,

Did you use 4-40 bolts to attach the JFETs to the heatsinks? Do you recall how long they were? What are you using to insulate the JFEts from the heatsinks?

I've got a pile of F5 parts scattered about my house. The case and especially dealing with the heatsinks have been the most imposing thing for me.

Oh, I used 4-40 to hold the fets, I got them just long enough to leave enough threads for a nut to be attached, and washer.

Russellc

Russellc · « **Reply #64 on:** 25 Feb 2011, 03:14 am »

Well, the 68,000 uF, 75 volt caps came but they are really big! 3+ inches in diameter and 6+ tall......wont be using the Daniels power supply boards with those. We'll see, they'd always be good for something even if not here.

Transformer ordered, Antek # AN-5218. Like I had planned, its a 18 + 18 volt 500VA unit. I'll order heatsinks in the morning, then contact Westend about case parts. Likely be 6061 aluminum again, works well.

On the resistor front I think I have decided on the Caddock MK 132 for the critical locations and Mills for the higher watt locations. Again, no current limiting circuitry here like my first build, so parts count is VERY low. Still, I dont think I can talk my self into the 17.00-27.00 USD price per part for the naked Vishays.

That's all for now

sts9fan · « **Reply #65 on:** 10 Mar 2011, 03:21 pm »

I will finally be getting mine together in the next week or so. I had to place one last order with digikey (why can't I get everything at once?). It SHOULD go together pretty easy. I am doing the PS P2P with two 68000uF caps per side. I did cheat and buy a case.

Russellc · « **Reply #66 on:** 12 Mar 2011, 04:33 pm »

Glad to see another build, thanks for posting here. I'm held up as M&M metals has substantially raised their prices, (I know metal is up but this is ridiculous and out of line with other suppliers pricing), I dont think they are interested in small order, with people I know having tried for pricing on 10-20 pairs and didnt budge.

The chassis measurements, especially for the 1" x 2.0" angle aluminum that forms the corners and fastens together the heatsinks to the front and rear panels, are necessaryn first. The height and length of the sink are both necessary. The heatsink height determines the height of the amp and so forth.

Until I decide on sinkage, which should be shortly, I'm in stall mode. I have aquired (and used same previously) the boards for the power supply and amps, Have aquired the transformer, and other parts needed to determine how much real estate is needed inside the case. I just need to determine heatsink to be used before aluminum can be cut....Be back in short order.

Russellc

Russellc · « **Reply #67 on:** 12 Mar 2011, 04:41 pm »

Quote from: sts9fan on 10 Mar 2011, 03:21 pm

I will finally be getting mine together in the next week or so. I had to place one last order with digikey (why can't I get everything at once?). It SHOULD go together pretty easy. I am doing the PS P2P with two 68000uF caps per side. I did cheat and buy a case.

DID you score the same 68,000 75 volt caps I did from a DIYAudio member? I wondered if these may be overkill, but my first F-5 used a bout half as much on each (Of two) power supplies, so total capacitance is about the same as my last build, but that was dual mono with 2 400 VA transformers, this time is a single 500VA transformer....100 VA less, hopefully it can do it.

Otherwise I'll buy the same 33,000 uF caps I bought last time and mount them on a Paul Daniels board I guess. Do you have any pics? My caps are big blue monsters, I almost think I should save them for a larger build, (aleph) we'll see. You've got me thinking about using them again!

Russellc

sts9fan · « **Reply #68 on:** 14 Mar 2011, 02:39 pm »

Quote

DID you score the same 68,000 75 volt caps I did from a DIYAudio member?

I did get mine off DIYaudio but over a yerar ago. They are 65V jobbies

Quote

I wondered if these may be overkill

I don't get this? Is there such a thing?

Quote

but that was dual mono with 2 400 VA transformers, this time is a single 500VA transformer....100 VA less, hopefully it can do it.

http://www.diyaudio.com/forums/pass-labs/121228-f5-power-amplifier-408.html

You will be totally fine. I think the FirstWatt comes with a 300VA or 400VA. I had an extra 300VA 2*18V so I am gonna use it. If I think I need bigegr I will order one.

Russellc · « **Reply #69 on:** 14 Mar 2011, 04:16 pm »

You are correct, I believe the original FirstWatt F-5 uses a single 300VA 18+18 If I recall

. 250VA woud likely be adequate as well. These Anteks are so affordable! And I do like transformer overkill!

Russellc

sts9fan · « **Reply #70 on:** 14 Mar 2011, 04:30 pm »

I agree. I am trying to be good and use what I have. So that means overkill for the PS caps and 300VA for the tansformer. I guess that averages out to just right.

Russellc · « **Reply #71 on:** 14 Mar 2011, 05:21 pm »

What are you using for sinks?

Russellc

sts9fan · « **Reply #72 on:** 14 Mar 2011, 05:26 pm »

The big Conrads. Its what I used with my ZenV9 and they are nice looking.

strider · « **Reply #73 on:** 18 Mar 2011, 04:01 am »

Got my boards populated this morning and wired it up about 3 hours ago. Powered it up and blew the fuses immediately. Not real good at fault tracing this stuff, I started by unhooking wires and seeing how far into the circuit I could leave hooked up and not have it blow. From the IEC inlet I can get to having it hooked up to the bridge rectifiers and be ok. Hook up the PS board to the rectifiers and power up and fuses blow. Knowing this, I started unhooking power wires from the amp boards, still blowing. To me it seems to be something in the PS board. I don't see anything shorting. Any thoughts on how I should narrow down the problem?

Thanks in advance,
Ben

Russellc · « **Reply #74 on:** 18 Mar 2011, 01:26 pm »

Pics? I didnt even use fuses when I powered up, but I did so with a variac,
measuring and watching for anything to overheat. You used those gigantic caps, right? Maybe there is just an inrush sufficient to blow the fuse? I know there are the thermistors that help with inrush, but those giant caps look like a dead short when first hit with the juice? Just thinking out loud. Lets see this beast and then we'll measure a few points. It is easy to miswire the rectifiers...

Russellc

strider · « **Reply #75 on:** 18 Mar 2011, 01:33 pm »

Here are a couple I took this morning:

sts9fan · « **Reply #76 on:** 18 Mar 2011, 02:08 pm »

I don't see anything but I am not sure I like the boards hanging from the MOSFETs

strider · « **Reply #77 on:** 18 Mar 2011, 02:23 pm »

Thank you for taking a look.

The board mounting isn't final, I've got stand offs for them but need to rethink how I'm using them. The heatsinks are mounted to the sides of the case and the bottom of the case is pretty flexible. When standoffs are attached to the board, the bottom flexes enough to make the boards move up and down at the legs of the MOSFETs. When I've got the fuse thing sorted out I need to figure a way to sure up the boards to the heatsinks rather then the bottom of the case.

Quote from: sts9fan on 18 Mar 2011, 02:08 pm

I don't see anything but I am not sure I like the boards hanging from the MOSFETs

strider · « **Reply #78 on:** 18 Mar 2011, 02:29 pm »

I am using Panasonic 15000uf 35v caps, 8 of them, in the PS board from cviller on diyAudio. The power supply as a whole is straight out of the schematic in the F5 manual from PassDIY. Thermistors at the negative lead of one primary and the positive lead of the other.

Quote from: Russellc on 18 Mar 2011, 01:26 pm

Pics? I didnt even use fuses when I powered up, but I did so with a variac,
measuring and watching for anything to overheat. You used those gigantic caps, right? Maybe there is just an inrush sufficient to blow the fuse? I know there are the thermistors that help with inrush, but those giant caps look like a dead short when first hit with the juice? Just thinking out loud. Lets see this beast and then we'll measure a few points. It is easy to miswire the rectifiers...

Russellc

Russellc · « **Reply #79 on:** 19 Mar 2011, 02:28 am »

I see, and really dont spot anything right off the bat, looks neatly wired
and correct. I really cant tell the orientation of the diode bridges, but can only assume they were wired correctly, you seem to had good attention to detail.

I was thinking you used some large can caps and hardwired your power supply, I'm mixing your build up with another. The Cviller boards are straightforward so you should not be having power supply issues.

I'm sure you thought of this when wiring, but I have seen more than one F-5 builder mix up the wire pairs on the secondary side of the transformer. They cant be mixed and its easy to do. I'm sure you were on to this when wiring up. Use your mulitimeter to test for continuity to match them up. Again, I'm sure you thought of this already.

The outputs look a little uncomfortable, but I dont know that its a problem, you definitely want to avoid stressing the leg/fet junction. the boards weigh very little and can hang dead bug style. I would have the mosfets legs out 90 degrees and hung the board like a picture frame.

There is no problem mounting them on standoffs from the bottom of the chassis and even using wires to the mosfets, as long as they dont exceed 12 inches, which would be way more than enough.

Perhaps fire up with a variac, and if the fuse still pops, measuring everything until the place where it is off is found.

Russellc