Prototypers wanted

[Pars]

My brother brought the rest of the parts over yesterday, so I got started on building this.

Looking at the MUR810s, I assume that the tabs of D5 and D6 touching each other would not be a welcome occurrence? Anyone do anything to safeguard against this happening?

[dsavitsk]

Anyone do anything to safeguard against this happening?

Yes, when you put the legs through the holes in the circuit board, melt a little solder on the juncture to hold them in place.

[Pars]

Yes, when you put the legs through the holes in the circuit board, melt a little solder on the juncture to hold them in place.

Oh... you're supposed to use solder on these? With heat?

Seriously, for the production run or whatever, this could be a concern. If someone can f something up, they will. Poking around on the board, etc., they could be bent into contact with one another. The caps protect them somewhat.

[kevin gilmore]

2 inch long #4-40 nylon screw and a few nylon nuts.

holds the diodes in place, no chance of a short.

[Pars]

Yeah, that would work. Probably just one shorter nylon screw and nut on the end diode would suffice.

What might work better would be to use some fullpak diodes, which are insulated. The MUR series doesn't offer them other than the MURF860G. I've used some Fairchild Stealth diodes from Mouser before in a sigma22 (the one on my dynahi) which use this package. Most layouts don't put these diode packages in back to back, but keep the orientation the same (sigma22 for example). Just pointing out a potential problem once these kits are released into the wild, as I could easily bend the two into contact with each other, intentionally or not. Because of the heat issues, there is also more likelihood of peeps running these without the tops on, so more chances of fingers getting in there.

[Pars]

Mouser 512-ISL9R860PF2

ISL9R860PF2 Fairchild Semiconductor Rectifiers

These are the Stealth rectifiers that I have used. TO-220F package.

[luvdunhill]

Doug:

Is there any way the brightness of the cathode LED could be related to the input frequency? Over the weekend I played a test track through it (One of the Ayre test disc (white|pink|brown) noise tracks) and noticed the cathode LEDs doing a little dance throughout and figured that might be relevant.

[dsavitsk]

Doug:

Is there any way the brightness of the cathode LED could be related to the input frequency? Over the weekend I played a test track through it (One of the Ayre test disc (white|pink|brown) noise tracks) and noticed the cathode LEDs doing a little dance throughout and figured that might be relevant.

Sure. If there is a big signal swing on the grid and a lot of the current is being delivered to the load, the LEDs current should change with signal. I'd think it would need to be really low frequency to see.

[luvdunhill]

in this case the signal is "all frequencies". sorta interesting to watch. I'll see if I can post a sample that does it.

[Fitz]

Just got my parts to start assembling this, except the switch. I found another one than in the BOM since it was out of stock, except I didn't look closely at the datasheet and it's a momentary switch. Mouser description says On-On, datasheet correctly says On-(On). Dammit.

[n_maher]

Fitz, point out the mistake to Mouser, they'll likely send you the right switch without having to ask.

[Fitz]

Good idea, I'll try that.

[Fitz]

I'm thinking the R5L/R and R6L/R positions should be lengthened to .7" if the board will allow, to match the other 1W resistors (R2 & R3).

[Pars]

Got the amp built and casing partially done (back panel). I tried to move all panel components as far forward or backward as the case may be in order to compensate for the case length, including partially straightening the pot pins to move it forward a bit. Same with the switch. The RCA jack on the template seems slightly high, though it could very well be my placement of the template on the panel

MJEs are running around 70

[luvdunhill]

Chris:

The issue with the RCA jack IMHO is that the securing hole interfers with the securing hole on the IEC, so the entire RCA jack leans a bit and causes the template to be off. Any chance you could verify the location of the pot and antirotate point on the front panel when you get around to those, I've sorta been waiting for another person to chime in before I attempt it.

Doug:

I was wanting to up the gain while I'm in there to up the current as you recommended above. Any recommendations here? I don't have a single can that I use below 70% of the pot and all in fact are comfortable at 100% if the source material is recording at a low level. My source is 2vrms output and cans are all (properly damped) orthos.

[dsavitsk]

PL is 130Vdc and PR is 110Vdc. Not sure why the difference between channels.

Not surprising, though if they were matched then you might want to check the CCSes or the bias.

Using 75 ohm R4s. Jumpers are set for CCS (all 4).

Jumpers set the bias -- CCS is always on.

I was wanting to up the gain while I'm in there to up the current as you recommended above. Any recommendations here? I don't have a single can that I use below 70% of the pot and all in fact are comfortable at 100% if the source material is recording at a low level. My source is 2vrms output and cans are all (properly damped) orthos.

Gain is what it is. It is slightly adjustable depending on the impedance of the bias and the amount of current, but not enough here that you'd ever notice. I have my doubts that this is appropriate for orthos, though there is no reason to not turn the dial up to 70 or 100%.

[ATTACH=CONFIG]3386[/ATTACH]

[Pars]

Chris:

The issue with the RCA jack IMHO is that the securing hole interfers with the securing hole on the IEC, so the entire RCA jack leans a bit and causes the template to be off. Any chance you could verify the location of the pot and antirotate point on the front panel when you get around to those, I've sorta been waiting for another person to chime in before I attempt it.

Marc:

I drilled the front panel tonight. The pot and the jack positions are fine, including the antirotate nub. The switch was a little high (template) compared to the actual switch. If I were to do it over, I would make a slot (vertical) for the toggle only to come thru. The switch sits back so the barrel of the switch does not stick thru or touch the front panel.

On the rear, I haven't had a problem with the RCA jack screw versus the IEC screws, but I haven't put them both in yet. Hmmm, will have to take a look. By eye, it appears that the case is pretty much 2x the thickness of the plastic end spacers too short. I will need a washer behind the jack and the pot. Better as Kevin said to slide the PCB all the way back so the RCA jacks fit properly.

Not surprising, though if they were matched then you might want to check the CCSes or the bias.

Jumpers set the bias -- CCS is always on.

OK. I didn't do any matching. Voltage moved with the tube, so I guess it is what it is. I replaced the heatsinks with some extras from my Gilmore V2 build. Mouser 532-563002B00. I mounted them upside down, and will cut the tabs off. BJTs were running around 50-51

Edited July 20, 2010 by Pars

[Pars]

^ too long (the case, that is)

[n_maher]

Marc:

I drilled the front panel tonight. The pot and the jack positions are fine, including the antirotate nub. The switch was a little high (template) compared to the actual switch. If I were to do it over, I would make a slot (vertical) for the toggle only to come thru. The switch sits back so the barrel of the switch does not stick thru or touch the front panel.

I suppose if any one is going to I should probably have a go at the "slot" approach. I got the vise on the mill tuned last night so it's now at least theoretically possible for me to be accurate with it.

[luvdunhill]

Marc:

I drilled the front panel tonight. The pot and the jack positions are fine, including the antirotate nub. The switch was a little high (template) compared to the actual switch.

yeah, I was curious about that, hence the question somewhere on the previous page about the measurement used for the top of the board to the bottom of the panel...

[Nebby]

It seems like the RCA jack is tipped ever so slightly due to the spacing with the IEC. I was thinking of simply sanding down the plastic on the RCA jack but I'm not sure the screws would fit if I did.

[dsavitsk]

It seems like the RCA jack is tipped ever so slightly due to the spacing with the IEC. I was thinking of simply sanding down the plastic on the RCA jack but I'm not sure the screws would fit if I did.

Guys -- there is a fair amount of play front to back in the IEC -- the holes in the board are round, but the pins are wider than they are deep. If you are having issues lining things up, you might try desoldering the IEC, then use the cutout back to line things up, then resolder it. As a general rule, if you have multiple board mounted parts to line up on a panel, it is always easier to mount them to the panel first, then solder.

[Pars]

That is kinda what I did on mine, though your suggestion to mount the components to the panel first is a good one... why didn't I think of that

Oh wait, I didn't have the panel cutout yet.

BTW, I may come up with some extra panels if anyone needs an extra one. I'll let you know if these magically appear or not.

[Nebby]

I was so eager to give the thing a listen that I didn't do the panels first. I guess next time I'll do them first

[Pars]

Regarding the voltage imbalance between PR and PL that I was seeing (130Vdc vs. 112Vdc): I swapped tubes and it moved with the tubes, and stayed the same voltage-wise, so I guess I can conclude that it is the tube matching and not CCS matching causing this. I guess I can also conclude that the amp is working correctly? I'll finish casing it and go from there.

BTW, I was missing one of the feet for the case, but I guess I can find something else that will work fine.