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New Millett Hybrid Maxed Amp - Page 101

post #1501 of 6564
9/11/07 at 8:26am
OK, makes sense - nice work on the mask, btw.
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post #1502 of 6564
9/11/07 at 9:34am
Quote:
Originally Posted by adfinni View Post
Does anyone in the US have a pair or two of those transistors that they would be willing to ship over to the UK for a price, as i contacted B&D enterprises who confirmed the minimum $50 international order amount. Im not ready to spend that much as the costs for my boutique are spiralling out of control anyway

Anyhow, ordering my bits from mouser, and every other supplier around the world this week, so should hopefully be building by the end of next week.
I should have an extra pair around here somewehre
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post #1503 of 6564
9/11/07 at 9:59am

2SC3422/2SC1359

Would anybody have an extra set of 2SC3422/2SC1359 to spare, I would really like to try those. BDent don't have the 2SC3422 in stock... I just ordered a kit from Jeff Rossel and I really look forward to build this amp.

Thank You
Bou

Edit : I forgot to say, I can pay with paypal for the transistors and the shipping to Canada.
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post #1504 of 6564
9/11/07 at 10:10am
Quote:
Originally Posted by bou View Post
Would anybody have an extra set of 2SC3422/2SC1359 to spare, I would really like to try those. BDent don't have the 2SC3422 in stock... I just ordered a kit from Jeff Rossel and I really look forward to build this amp.

Thank You
Bou

Edit : I forgot to say, I can pay with paypal for the transistors and the shipping to Canada.
check with Soloz2 above. I'm committed to Adfinni and a couple of others right now and am running low myself. If that falls through, send me a PM and I'll see where I stand.
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post #1505 of 6564
9/11/07 at 10:24am
Thank you Tomb for the response. I will contact soloz2.

Soloz2 YGPM.

Bou
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post #1506 of 6564
9/11/07 at 10:33am
Quote:
Originally Posted by soloz2 View Post
I should have an extra pair around here somewehre
Thanks for the offer, but ive already sorted it out with tom
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post #1507 of 6564
9/11/07 at 5:59pm

Food for thought

Quote:
Originally Posted by c0nsumer View Post
A while back I did a write-up on how I remove flux from PCBs. If you want to read it, it can be found here:

Flux Removal

More specifically, what I did for the MAX soldered with a lead-free solder with Kester 331 (and 2331-zx) was as follows:

- Solder down everything except the volume pot and one of the two center heatsinks. Also leave out other non-sealed parts if you have any. For the MAX I also left the MOSFETs off at this stage, because I didn't want water seeping in between them and the insulating film via capillary action.
- Scrub the board down with warm tap water and a toothbrush. (I do this in the laundry tub.)
- Rinse the board thoroughly.
- Rinse the board with distilled water.
- Dry the board with a combination of hot air (to dry faster) and compressed air (to get water out of small crevices).
- Solder the volume pot, fit all the MOSFETs (BJTs would also apply here) and final heatsink.
- Use a towel dampened with distilled water to remove the new bits of flux.

This is similar to what is used in many test labs, except they'll often have an automated system which is water with cleaner, plain water, then deionized water.

Also, I'm not sure if it was noted here already, but I've seen flux conduct just enough to trigger FETs and other parts, causing all sorts of problem. Not to mention that flux is generally corrosive...
Ever heard about Electro Static Discharge (ESD)? Especially water: water can be regarded as a good conductor ( = electrons/charges transfer). What described here (use a towel to remove flux... ) may generate charges transfer that are potentially harmful to sensitive components (MOSFETs, transistors) mounted on the board.

ESD damaging of sensitive components is not always visible directly as toasted MOSFETs/transistors or somthing like that, but it can be latent also... things to keep in mind.
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post #1508 of 6564
9/11/07 at 11:33pm
Quote:
Originally Posted by tomb View Post
OK, makes sense - nice work on the mask, btw.
Ok, time to bias those DBs and give the full sonic evaluation. The mask is being worked with Paint Shop Pro, as opposed to the "proper" electronics software. It is in some ways more difficult, but in many ways easier for me to use.
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post #1509 of 6564
9/11/07 at 11:45pm
Quote:
Originally Posted by amphead View Post
Ok, time to bias those DBs and give the full sonic evaluation. The mask is being worked with Paint Shop Pro, as opposed to the "proper" electronics software. It is in some ways more difficult, but in many ways easier for me to use.
This is a pretty simple board. Laying it out again in EAGLE wouldn't be too difficult, but the license to do a schematic+board of that size runs US$800.

I'd gladly do it, but I only have a commercial license for 80mm x 100mm boards, and a non-profit license for 160mm x 100mm.
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post #1510 of 6564
9/12/07 at 12:45am

Still no dice with my MAX

RA8L and RA9L check out just fine.

RA1L checks out ok too.

Replaced QA1L and QA2L.

Replaced the tube socket.

Whereas before i could bias VTL between about 7.6v and 8.5v, now i can bias it between about 9.5v and 10.4v.

Anybody got any ideas?


Mosfets aren't biasing the way they ought either.

I got proper 1n5486's into QB1L/R. RB12L/R are 1k as specified.

There's a point on both sets of mosfets where, when rotating RB12, the voltage between TA2 and TB1/2 jumps from 30mv to over 1v.

I've never had this much trouble with a printed board amp before.

Edit: Oh, using the min/max function of my Wavetek DMM, i've measured the inrush at as high as 1.7 amps. These fast-blowing fuses don't have a snowcone's chance in heck.
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post #1511 of 6564
9/12/07 at 6:17am
hm. is that with the tubes in? what happens when you switch the tubes between L/R? does VTR bias right? do you have a function to check diodes with your dmm? go over all the transistors and make sure you have 2 diodes in them.. with about 0.3~0.8v forward bias voltage(I dont think you can check the mosfets with your dmm so simply though). just look at the NPN as 2 diodes, NP and PN. the PNP as PN and NP. when you initially fired up, what were the trimmers orientation? other than caps, did you get any parts not from the BOM?
got pics?
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post #1512 of 6564
9/12/07 at 8:14am
Quote:
Originally Posted by ericj View Post
RA8L and RA9L check out just fine.
Just to be sure, RA9L must be 10 times RA8L. The BOM specifies:
RA8L: 1.13K ohm
RA9L: 11.3K ohm

Alternatively,
RA8L: 1K ohm
RA9L: 10K ohm

So, are your values similar - or do you have "K" values?

Quote:
RA1L checks out ok too.
Just for kicks, is this trimmer 5K? The PS trimmer is 2K, BJT trimmers are also 2K, the MOSFET trimmers should be 1K. However, the tube trimmers should be 5K.

Quote:
Replaced QA1L and QA2L.
Are these both 2n5087's? They are both the same, not a complementary pair.

Quote:
Replaced the tube socket.
I doubt that had anything to do with it, IMHO.

Quote:
Whereas before i could bias VTL between about 7.6v and 8.5v, now i can bias it between about 9.5v and 10.4v.
Almost sounds like the wrong trimmer to me - just a guess.

Quote:
Anybody got any ideas?
See the above.


Quote:
Mosfets aren't biasing the way they ought either.

I got proper 1n5486's into QB1L/R. RB12L/R are 1k as specified.
Just for the record, they should be 2n5486's, but I'm sure that's a typo.

Quote:
There's a point on both sets of mosfets where, when rotating RB12, the voltage between TA2 and TB1/2 jumps from 30mv to over 1v.
Again - just asking the obvious - but do you have the MOSFETs on the left side of the sinks as you face the front of the board? Are RB1L/R jumpered out? These are not used for the MOSFETs. Are you using R84L/R and RB9L/R? These should be 100ohm, but are not used in the BJT version. Are RB2L/R and RB3L/R 390ohm? These values of RB2 and RB3 are unique to the MOSFET version. Finally, are RB12L/R 1K trimmers? Again, this value is unique to the MOSFETs.

Quote:
I've never had this much trouble with a printed board amp before.
Sorry for your trouble.

Quote:
Edit: Oh, using the min/max function of my Wavetek DMM, i've measured the inrush at as high as 1.7 amps. These fast-blowing fuses don't have a snowcone's chance in heck.
No comment.
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post #1513 of 6564
9/12/07 at 8:51am
Quote:
Originally Posted by ericj View Post
Edit: Oh, using the min/max function of my Wavetek DMM, i've measured the inrush at as high as 1.7 amps. These fast-blowing fuses don't have a snowcone's chance in heck.
I'm not trying to stir up discussion over this, I just wanted to mention Mouser part number 576-0218001.HXP which is a slow-blow 1A fuse whose datasheet seems to indicate that it can sit at just over 2A for a bit more than one second. I ordered a few of these and I'll see how they work out. I presume the results will be good. I also ordered the 800mA analog for the new BJT MAX I'm putting together. I'll provide inrush and such for that one once it is complete.

-Steve
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post #1514 of 6564
9/12/07 at 12:00pm
Quote:
Originally Posted by ruZZ.il View Post
hm. is that with the tubes in? what happens when you switch the tubes between L/R? does VTR bias right?
Yes. Whatever tube is in the right socket biases fine. These are United 12FM6 tubes I've used in my RevMH.

Quote:
Originally Posted by ruZZ.il
do you have a function to check diodes with your dmm? go over all the transistors and make sure you have 2 diodes in them.. with about 0.3~0.8v forward bias voltage(I dont think you can check the mosfets with your dmm so simply though). just look at the NPN as 2 diodes, NP and PN. the PNP as PN and NP. when you initially fired up, what were the trimmers orientation? other than caps, did you get any parts not from the BOM?
got pics?
I guess i could check the transistors that way.

Trimmer orientation is correct.

Several caps aren't identical to the BOM but that's to be expected. R1 is 20ohm but since V+ is 27.8v that's fine.

RA5C and LEDC are not populated.

Bridge rectifier is built with ultrafast to220 diodes you've never heard of, but that's ok.

Quote:
Originally Posted by tomb View Post
Just to be sure, RA9L must be 10 times RA8L. The BOM specifies:
RA8L: 1.13K ohm
RA9L: 11.3K ohm

Alternatively,
RA8L: 1K ohm
RA9L: 10K ohm

So, are your values similar - or do you have "K" values?
RA8L reads 1.146k, RA9L reads 11.45k.

Quote:
Originally Posted by tomb
Just for kicks, is this trimmer 5K? The PS trimmer is 2K, BJT trimmers are also 2K, the MOSFET trimmers should be 1K. However, the tube trimmers should be 5K.
They are Murata type PV36 5K trimmers. I've measured from pin 2 of the tube socket to ground while adjusting it, and i have full range of adjustment between 0 and 5k.

Quote:
Originally Posted by tomb
Are these both 2n5087's? They are both the same, not a complementary pair.
Yup.

Quote:
Originally Posted by tomb
I doubt that had anything to do with it, IMHO.
I figured there was a possibility that I'd fouled something while gluing the halves together after drilling out the rivet.

Quote:
Originally Posted by tomb
Almost sounds like the wrong trimmer to me - just a guess.
Yeah, but it aint.

Quote:
Originally Posted by tomb
Just for the record, they should be 2n5486's, but I'm sure that's a typo.
Right. i don't think 1n5486 even exists.

Quote:
Originally Posted by tomb
Again - just asking the obvious - but do you have the MOSFETs on the left side of the sinks as you face the front of the board? Are RB1L/R jumpered out? These are not used for the MOSFETs.
Yes and Yes.

Quote:
Originally Posted by tomb
Are you using R84L/R and RB9L/R? These should be 100ohm, but are not used in the BJT version.
Yup. They look like 100r to me (have the right bands).

Quote:
Originally Posted by tomb
Are RB2L/R and RB3L/R 390ohm? These values of RB2 and RB3 are unique to the MOSFET version. Finally, are RB12L/R 1K trimmers? Again, this value is unique to the MOSFETs.
yes, and yes.

I'll post pics after work.
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post #1515 of 6564
9/12/07 at 12:10pm
Quote:
Originally Posted by ericj View Post
<snip> ... I'll post pics after work.
Yep. Based on your answers, that's the next step. Again, sorry you're having trouble.
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