[Televator]

Quote:

Originally Posted by Ferrari /img/forum/go_quote.gif Take a look at this shop.

looks interesting they do also offer 2234/986 pairs (5 pairs) combined for about the same price... must remember this for if I manage to fry some of my current ordered ones (forgot to order spares

)

 

[jerrygp]

Quote:

Originally Posted by Ferrari /img/forum/go_quote.gif Take a look at this shop.

Thanks Televator and Ferrari...I ordered 10 of the set from ALLPARTSPIPE on Ebay October 9th, but have yet to receive them. They are attempting to locate my order, but no luck yet. Coming from Hong Kong, I may be out of luck. I will try RS Components Europe though, and see what happens...I'm really wanting to try that configuration with the BG setup in this build.

 

[Possede]

Quote:

Originally Posted by willisv /img/forum/go_quote.gif Did you get the right tube bias trim pot mixed up with the power supply trim pot? It kinda looks like a glass jar kit that I just built.

Yeah, I bought this off of Jeff.

Great guy.

Since this is theoretically my first time building anything, I am virtually uneducated when it comes to circuits. I'm pretty sure the problem with the amplifier is an obvious mistake - on my part. Thanks for pointing that out - I just realised that the right side pot is a different colour to the rest, so should I swap it with the power supply's pot so they are both equally the lighter blue colour?

Does it matter that I am running it off of a 20V DC power supply? It's the only one I could find in my house at the moment.

 

[tomb]

Looks like some of these posts are messed up after the Head-Fi rebuild. I believe Naamanf stated that the 20VDC power supply is a problem before Possédé posted that he was using it.

It's worse than that, though: 20VDC will not be enough to support the minimum voltage requirement on the tube heaters. It's possible that the tubes will be damaged if you run them on that. You need 24VAC, minimum.

A couple of you guys need to verify those trimmers - it looks like some Vishay-BC's(?) are mixed up with some Muratas. It's possible that Jeff used different brands for trimmers with the same rating, but it looks confusing.

Post again if you are still having problems.

 

[tomb]

Here's another Millett MAX that I finished last week. This one is equipped with Black Gates on the signal positions with Russian K42's bypassing the output Black Gates. The BJT Diamond Buffer output uses 2SC2238/2SA968 complementary pairs. The switch on the left of the frontplate is a two-position Low-Z/High-Z switch. There is also a set of pre-amp outputs on the back that are switched from the headphone jack (OFF when a headphone is plugged in).

The tip jacks cover all of the important test points - Gnd, V+, L&R tube bias, and L&R DB bias. There are adjustment holes in the top plate so that all of these settings may be adjusted without taking the lid off.

In the past, I've stayed away from Black Gates because of the price and hype, but they really sound great. They took about 40-50 hours before they stopped sounding very "congested," however. Another 50 hours and they sound very, very nice.

[size=xx-small](click for larger pics)[/size]

 

[naamanf]

Looks great TomB! I have a bunch of the those Russian PIOs on the way. I look forward to trying them in my MOSFET Max.

 

[tomb]

Quote:

Originally Posted by naamanf /img/forum/go_quote.gif Looks great TomB! I have a bunch of the those Russian PIOs on the way. I look forward to trying them in my MOSFET Max.

Thanks, Naamanf! So, are you in CO or Iraq?

 

[naamanf]

Iraq. I imagine thats why it's taking so long for those caps to get here.

 

[tomb]

Quote:

Originally Posted by naamanf /img/forum/go_quote.gif Iraq. I imagine thats why it's taking so long for those caps to get here.

Not really - I only got mine Friday and I think several of us ordered them at the same time. (EDIT: my first ones came from fordgtlover!) They came wrapped up in several layers of brown paper with tape and stickers that had cryllic Russian writing all over it - weird/old and interesting at the same time. The caps look great, though.

Anyway, thanks for what you guys are doing for us over there! Shoot me a PM if you need any MAX parts - really.

 

[ruZZ.il]

And on another note.. nice box, tom! I've been running a similar config for the last week or 2.. good stuff.

 

[Bigguy]

Tomb, what is the switch on the front panel for? 2 inputs?

 

[tomb]

Quote:

Originally Posted by Bigguy /img/forum/go_quote.gif Tomb, what is the switch on the front panel for? 2 inputs?

It's a dual-impedance switch, switching between 10ohm and 47ohm Stackpole output resistors. It offers a minimum of attenuation adjustment while preserving most of the impact. Ordinarily, I like to run bare on output resistors, but this one is built for someone else and they wanted more useful travel on the volume knob.

 

[Televator]

well, this will be a pretty large post... in the style of the old-fashioned western: "The Good, The Bad and The Ugly"


The Good: my second Max is alive!

It'is a Black-Gates version with Russian K42Y PIO bypass caps (used at CA8 & CA9), Pana FM 1800µ's at CA4&5 and 2SC2238/2SA968 transistors. I still need to replace the V-D resistors at RB14 by Kiwame's...

Leds are high intensity Orange (amber) leds raised to sit in the hole of the tube sockets, which gives a great glow-effect. As for now it isn't cased yet (still thinking on the case).

It has been running for a couple of days straight to burn in the caps/tubes and it already sounds great (even from a bad Panasonic PCDP hooked up through gator-clips

I'll be hooking up some neutrik RCA-sockets soon so I'll be able to test it with my NAD CDP... but I'm very confident it'll sound amazing!

Just a quick few pics...

The Bad: my first Max has died!

I got hold of some 2SC3422/2SA1359 transistors (thanks Tomb!) for my Muse KZ version. I installed them without any problems and ran it for a couple of days. This version (with 480µ KZ's + WIMA's all around as in the Jrossel/glassjaraudio-kit) sounded "mucho fun" with those BJT's!

However I had ordered some extra tubes for backup and wanted to test them to see if none were DOA (see further). As my KZ-version is fitted in the second Hammond slot from below, switching tubes isn't that easy when cased up...so I opened her up for a while. I unfortunately didn't screw the back-plate back on after removing the top and one of the test-points (TBR2) shorted with the case (=ground) through a badly isolated screw on the probe-socket in the back-panel... I saw a bright spark at the short-location, heard a pop and my Max was dead!

I haven't found the guts to try and turn it back on, because I guess that it wouldn't help anyway and I might damage it further doing so. So my question is what parts have been fried (BJT's? How many? other parts?...) and if there is no sure answer to that (which I guess there isn't) how I can check this myself without replacing stuff blindly (no visual damage at all but I can always take some pics anyways). I have got a DMM with most standard functions, though no HFE...

Thank you all in advance for troubleshooting my sick Max!


The Ugly: you have got to love the postal services

As said above, I love the Max for my MS2i with 12FK6-tubes...so I decided to order some extra for back-up. The five tubes I ordered arrived pretty quickly given they had to travel from the US to Belgium... but unfortunately they arrived like this:

The tubes themselves (and their individual boxes) didn't look damaged... but I wasn't sure whether the innards had survived as well. I decided to test them ... but while my tubes are OK, I unfortunately killed my first Max testing them

 

[tomb]

Televator - a couple of things:

1. Did you incorporate a fuse? It's likely that burned out if you shorted something. I'm curious, because you say the MAX is dead. I would've thought something shorted and smoked in the right channel DB - probably the JFET or one of the small signal transistors. The power transistors can take a lot. They probably won't die unless you hooked them up backwards in the circuit and left them that way for an extended period (a few seconds?) - which you didn't do.

So, I guess I'd like some more details - crack that thing open, plug it up and start making measurements - do the test points first. For instance, do you get voltage on the PS, do the tubes light, what are the tube bias points reading, do any resistors look fried, etc., etc.? We may be able to figure it out, but it will take more information.

2. This is just an "oh, by the way", but the recommended way to mount those K42's is to clip the leads and solder on some hookup wire, silver or silver plated if possible. Even if you found a way to mount them with the existing leads, we're pretty sure they're magnetic - so you don't want them anyway.

If you use the leads and tombstone them, you'll find that in those back positions you can tombstone them in the two extra "Gnd" test points just behind the cap positions. Use a hookup wire length on top to snake around the front of the trimmers and solder into the "+" positions on the CA9 positions.

Just a suggestion - it depends on whether they're stable the way you've got them.

 

[dbfreak]

Great idea with the tip jacks and I look forward to the Millet Max board being offered for groupbuy again, one day.