and now for something completely different part 3

[Satyrnine]

8 hours ago, johnwmclean said:

FWIW with 2 X 100VA the GRLVs are not going to run hot, you can mount them to the base plate.

 

2 hours ago, audiostar said:

Not really going to work as there are caps on the GRLV boards. Maybe, with a 5U case 😎

The pass transistors you better mount directly to the bottom plate, like John has shown above. Oriented to center, straight below the Goldpoint stepper.

Well hell, wish I would have come across that photo earlier, haha! That sounds like a great solution. I'll set it up just like that. Thanks Guys!

[audiostar]

1 hour ago, Satyrnine said:

Well hell, wish I would have come across that photo earlier, haha! That sounds like a great solution. I'll set it up just like that. Thanks Guys!

Well, reading the threads always helps. There is a ton of information in there. 

[Satyrnine]

2 hours ago, audiostar said:

Well, reading the threads always helps. There is a ton of information in there. 

Oh I did mostly, or I definitely wouldn't have made it this far, haha! I must have missed this one or overlooked thinking I needed to heatsink mount them with 30v.

[audioguru1]

On 4/26/2023 at 8:20 PM, Pars said:

Yeah, that could work, though I'm not sure why everyone breaks taps? Are you tapping by hand or using a drill? By hand, do a couple of turns, back out 1/2 turn or so, continue, rinse and repeat. I've never broken a tap, even on blind holes with a bottoming tap.

 

This is very helpful advice. I will also add, that I broke a ton of taps until I realized....

1. I was using the wrong size drill bit. M3 requires a 2.5mm bit. Not a SAE drill bit that is close.

2. Impatient, and just kept pushing (spiral fluted taps help if you are in a rush like me)

3. Buying junk taps on amazon

[Satyrnine]

I started populating my grlv's tonight. I tested my MJF15030 and 31's and they vary quite a bit. I recall it said that matching isn't too terribly important, but want to double check. I know I'll get scolded, but I DID source the 30's from a seemingly legit and well reviewed ebay seller, since they are out of stock everywhere. I'm wondering if I got a batch of rejects. Here's what I found:

MJF15031 from mouser: All around 280hfe +/- 5.

MJF15030 from THIS ebay seller: 80-150hfe. Oof.

Visually they look identical, even with a loupe. I know that doesn't nec. mean much. Is this normal? If these are questionable, anyone have a source for 30's?

Also, the larger tantalums are 36v, not sure if they see full 30v or not, that's a bit too close to 30v if so. I ordered from an existing bom, and didn't catch this.

Edited April 29, 2023 by Satyrnine

[jamesmking]

1 hour ago, Satyrnine said:

 

MJF15031 from mouser: All around 280hfe +/- 5.

MJF15030 from THIS ebay seller: 80-150hfe. Oof.

Visually they look identical, even with a loupe. I know that doesn't nec. mean much. Is this normal? If these are questionable, anyone have a source for 30's?

 

almost no authorized seller except farnell has MJF15030G in stock at the moment.

Farnell has 347 https://uk.farnell.com/on-semiconductor/mjf15030g/transistor-npn-150v-8a-to220fp/dp/9556303

meanwhile the nonauthorized sellers claim to have about 300000 in total between them - I call BS...

using a atlas dca75 pro I get hfe values of 89, 79, 87, 87, 95, 91, 98, 75, 108 for the 9 in my current stock (from radio spares, all purchased at the same time) - known good and used in GRLV. test conditions are: Ic 5mA, VBE 0.675V IB 5mA NPN silicon BJT. Spec sheet says 40hfe minimum for sensible currents.. no range or max is given....

My MJF15031 (from mouser) measure much higher hfes than the MJF15030. hfe 265, 263,264, 270, 263, 265,265, 269, 264, 266. So im getting a similar difference in hfe between the 30s and 31s as you are and a similar spread of hfes.

Edited April 29, 2023 by jamesmking

[Satyrnine]

7 minutes ago, jamesmking said:

almost no authorized seller except farnell has MJF15030G in stock at the moment.

Farnell has 347 https://uk.farnell.com/on-semiconductor/mjf15030g/transistor-npn-150v-8a-to220fp/dp/9556303

meanwhile the nonauthorized sellers claim to have about 300000 in total between them - I call BS...

 

 

Oh wow, that must have been recent stocking! I just ordered from Farnell/Newark. Thanks! Definitely not something to risk.

[Pars]

I built and have a GRLV that I use for my DynaFET configured for +/-30V and have used it ever since I got the DynaFET running, so probably 4 years or so (would have to look at the thread). I'm pretty sure the tantalums are 35V and never had any problem with them. I'll look later today to confirm. I never tested the MJFs or MJEs (would have to look also to see), but bought them from Mouser as I do almost all of my parts. In process of casing it so it is torn apart right now.

[EL_Ken]

Just finished casing.
Case size 360*270*86mm (inner 280*255*73mm)

Dual GRLV ±30V
Extra DC supply for attenuator, relay boards and Protector.

Ship-in-bottle-like building experience with small cases and multi layer PCBs.
Some very soft cables would make it easier.

Difficult to adjust those trimpots on splitboards after casing.
Better to do the adjustment before casing.

Spider webs at the input state is a mess.
Better-designed PCBs can reduce half of the cables.
Will fix that after I get a new back plate and PCBs.

[audiostar]

Nice!

Miss the chassis pin on the three pin DC-In connectors, not a separate connector either. Chassis should go from the amp to the PSU case separately from circuit ground and make the connection to PE and circuit ground in the PSU case, close to the IEC inlet. Or how do you handle that? 

No ground to PE in the PSU case as well. Could be dangerous.

[EL_Ken]

1 hour ago, audiostar said:

No ground to PE

English isn't my native language.
Hope I didn't misunderstand your words.
That's mean don't connect circuit ground to PE, right?

PLT-163 connectors used for DC in/out.
3pins are +30V / circuit ground / -30V respectively, none of them connected to case.

I had once mis-connected circuit ground of GRLV to chassis, and killed the pass transistors.
So, I think circuit ground should not be connected to PE/chassis.
Now the whole system is floated from PE/chassis.
None of the circuit are connected to PE or chassis.

Sorry for my ignorance and please correct me if something wrong.

[Pars]

PE = Protective Earth (i.e., the ground on the IEC connector to building ground). That connection appears to be there on the PSU:

Edited May 3, 2023 by Pars

[audiostar]

Hi Pars,

yes, PE is connected to the case in the PSU chassis. But you connect there the amp's case as well - missing. 2nd, you connect there circuit ground as well (best is through a circuit breaker or via thermistor like Pass is doing or via 10ohm resistor like Kevin is doing). Then, the pass transistors are isolated from the case, so you don't get any shorts here. 

In his case the Amps chassis is not connected anywhere to PE. And in the PSU there is no connection from circuit ground to PE at all. 

 

[audiostar]

1 hour ago, EL_Ken said:

I had once mis-connected circuit ground of GRLV to chassis, and killed the pass transistors.

They must be isolated from chassis. Must use proper isolation. 

1 hour ago, EL_Ken said:

So, I think circuit ground should not be connected to PE/chassis.

Wrong, it must be connected. Now, it has do be done properly, so you do not get any hum. The moment you do something wrong and you get hum. And this applies all the way to XLR pin 1 and case wiring and so on. 

1 hour ago, EL_Ken said:

Now the whole system is floated from PE/chassis.

Not good. 

1 hour ago, EL_Ken said:

None of the circuit are connected to PE or chassis.

Even worse.

 

 

[EL_Ken]

Had done isolations between sands and heatsinks.
And then finish casing the PSUs (PE connected to case).
When I powerup GRLV alone, DC voltage goes wrong and pass transistors dead.
After checkings, I find GND on one of the GRLV shorted to case.
Top green insulation layer of pcb (near mounting hole)is damaged.
This short GND and case through screw.
So I thought that's the reason the transistors dead.
Maybe the transistors were damaged by desoldering, had to resolder them to fit the case.

But none of the circuit connected to PE will cause risk of electric shock.
And proper grounding can block out noise.

And I found some of your words said before.
 

On 3/5/2023 at 1:03 AM, audiostar said:

I tie pin1 to to the case immediately via the XLR connector (and not to ground) and use the metal case as shield. I use twisted wires for the signal inside the case. Circuit ground connects on a single place via a circuit breaker (at least 10ohm resistor) to the chassis. Gives me no hum whatsoever. 

Hope my drawing below is understandable.
GND: Splitboards > 10R resistor > amp case > extra wiring to PSU case > PE

[audiostar]

Connect amp's chassis to the same bolt where you have connected PE to the PSU case.

To this same point you connect both GRLV grounds, say via a 10ohm resistor. 

That's it, for now, for safety.

Measure and make sure there are no shorts between the pass transistors and the chassis. 

Then power on, play some music and check if you get any hum. 

[EL_Ken]

Thanks for you help.
Not yet powered my amp, will get some 10R and finish the grounding first.

[audiostar]

  Newer GRLVs have a place for a 10R directly on the board. 

Make sure you understand the AES48-2005 as well
https://usermanual.wiki/Document/ShieldWiringOfBalancedInputsAndOutputsAes482005F.2144015621.pdf

[Satyrnine]

A bit off topic, but I just have to say that this is the most knowledgeable, helpful, and BS free forum I've ever been a part of. Bravo everyone!

 

[swt61]

So, you haven't been here long enough to meet Brent?

[Satyrnine]

56 minutes ago, swt61 said:

So, you haven't been here long enough to meet Brent?

Haha, I guess not.

[Satyrnine]

Reading EL_Ken's post about grounding, (even though I know the incorrect grounding didn't cause a device failure in the end) I assume plastic shoulder washers are best to make sure boards don't ground to chassis through standoffs. Are brass or alum standoffs the best move, or would a nylon standoff/screw be a better option? I know it "depends" but does anyone have a suggestion for best size/height/etc for those?

Edited May 11, 2023 by Satyrnine

[audiostar]

11 minutes ago, Satyrnine said:

Reading EL_Ken's post about grounding, (even though I know the incorrect grounding didn't cause a device failure in the end) I assume plastic shoulder washers are best to make sure boards don't ground to chassis through standoffs. Are brass or alum standoffs the best move, or would a nylon standoff/screw be a better option? I know it "depends" but does anyone have a suggestion for best size/height/etc for those?

I am only using aluminium standoffs. If I don't need grounding, I just don't put pads on the PCB around the mounting holes. (If needed) I usually have a single hole only making contact to the case through the standoff for grounding. 

I also use female standoffs only. If I need a male on one of the sides, I add a male headless screw and some red of blue Loctite. Makes me keep less parts around.

The hight of the standoffs really depends on the application. Around 10mm is common. 

#4-40 or M3 is a good common size for the thread.

Edited May 11, 2023 by audiostar

[Pars]

The vast majority of boards do not have the board mounting holes connected electrically to anything (though you should always verify this). I usually use aluminum standoffs, either 4-40 3/8" or M3 10mm.

[kevin gilmore]

pretty sure all of my boards have the holes electrically isolated.