Hotrod Build Thread

[Greg]

Adam, I'm sorry I really meant a wiring diagram of your grounding scheme. So I can see what and where it's tied to your star ground.

 

[bluezplaya]

That's okay. I was feeling a bit artistic this morning, plus I have a nice new frame from Walmart I can put this in and hang in the bathroom.

I'll have to draw a grounding layout later, at 9am I have some recording to do.

Adam

 

[kato]

I printed it out and hung it on the fridge. :thumb:

 

[bluezplaya]

[/url]

 

[bluezplaya]

Sorry. Double post.

 

[madriaanse]

Wow, that's a lot of wiring! Are you getting feedback at higher gain? If you are you'll probably want to run all signal carrying wires through shielded cable (Canare L-4E5AT). This will also cut down on hum/emi/rfi garbage. Also, be sure not to connect any ground to the output XLR pin 1.

Hope that helps.

M.

PS I think you'll enjoy the simplicity of hooking up my EZ1290's!! :green:

 

[guavatone]

It looks like you are still wiring Chassis ground on the Hot Rod but it is really going to JLM 0 VDC . Disconnect chassis ground on Hot Rod and wire and connect it to 0V/Audio Ground on Hot Rod while the other end goes to JLM 0V-audio Ground. the I/P transformer chassis connection should still go to chassis.

 

[bluezplaya]

Once I get these right, I'll start working on stuffing your boards! However, I have yet to find the Grayhill switch available and never got a return email from Frank about the knobs :?

Adam
:sam:

 

[bluezplaya]

It looks like you are still wiring Chassis ground on the Hot Rod but it is really going to JLM 0 VDC . Disconnect chassis ground on Hot Rod and wire and connect it to 0V/Audio Ground on Hot Rod.

So just to confirm, the "Earth" ground from the Hot Rod's is actually 0v audio ground? What about pin 6 from the input transformers? That should be chassis ground, correct?

 

[guavatone]

No. Earth on Hot Rod is for earth but since u are using a JLM PSU u want to connect the Hot Rod audio Ground/0V to the JLM PSU. I am using Carnhills but and it has a pin that goies to chassis. Same with yours I think.


**** My PCMs are fermenting :grin:

 

[bluezplaya]

I'm so glad I can get some help on these because I've been itching to record with them. Question: instead of running a wire from the Earth of the hot rod boards to the 0v of JLM PSU, couldn't I just run that same wire to pin 5 of the input transformer because it is also 0v audio ground?

I mean, pin 1 on my XLR ins are grounded to PSU 0v, the XLR in's run to the Go Between switches, from Go Between to the input transformers, and audio ground is pin 5. So is it feasible to just connect to pin 5?

Thanks,
Adam

 

[Greg]

It seems that the grounding on this guy is tripping some people up, so I've got some docs that might help.

Grounding PDF:
http://members.cox.net/ram3n/1272/HotRod_Grounding.pdf

Reference picture:
http://members.cox.net/capstanrecording/1272/1272_Top2.JPG

Adam, make sure you're IEC GND in connected directly to the chassis at your star point. I didn't see this in your diagram (safety first).

Some notes (referenced to PDF above):

- Do no jump input and output XLR pin 1s together
- Jump input XLR pin 1s together and take to chasis star (not JLM 0V)
- Jump output XLR pin 1s together and take to chassis star (not JLM 0V)
- Notice that two seperate wires are going to chassis star (one for input and one for output)

- Connect input XLR pin 1s to 0V on Go-Between

- Connect 0V on Go-Between to pin 6 on 31267 (notice that the 31267 pin 6 has one path to chassis ground)

- Connect +24V and 0V from PSU to one Hotrod board and jump over to the provide power to the other Hotrod board

- Connect earth from one Hotrod board to chassis star. On this board, 10R 1W is needed. Remove 10R 1W from other Hotrod.

Hope this helps.

 

[Greg]

After looking at my diagram, the earth connection from the Hotrod board might not be needed at all because there is a 10R in parallel with a 0.1uF cap on the JLM PSU. So the 0V has a nice clear path to ground through that resistor/cap.

I used Bauman's PSU so the 10R on the Hotrod was needed.

Perhaps try it both ways.

 

[bluezplaya]

Dude, you rock. I will re-wire my grounding and double check everything. Joe Malone tells me that I might be getting too much current because my 12 ohm resistors are smoking. So to adjust the current I need to trim the 283's. Well those don't seem to trim much, so he says that one of the transistors has blown :shock: . I wonder if because of improper grounding I'm getting improper voltages elsewhere?

 

[bluezplaya]

Okay, I wired it up exactly like your diagram and I am passing fuzzy audio on both channels with HF osc.. And something on the PSU starts slowly smoking. Can't tell what it is. Looks like it is coming from behind it. Anyway, I must go to record another day without Neve . Oh well, I have a nice arsenal of 8 Baby Animals and 4 Green pre's but hopefully I can get this Neve working by the time I cut VOCALS!

See ya this afternoon

Adam
:sam: :sam: :sam:

 

[madriaanse]

Hi Adam,

Sorry to hear about the troubles.

Is your JLM PSU (ACDC?) working properly when it's not hooked up to your pre? You're getting +24 and +48 right? Got those LM317's heatsinked properly?

Also sounds like you might have a fried 2N3055. The HF oscillations could come from having a faulty 2N3055 and/or not using shielded cable. I would try replacing 2N3055 and the parts surrounding it.

I believe Neve calls for pin 6 on the input transformer to go to chassis, but when I experimented around with this I think I got a better noise figure connecting pin 6 to 0V. See: http://musiciansgig.com/ez1290/assembly.pdf

I like Greg's grounding scheme, but I take it one step further and leave pin 1 disconnected on the output alltogether to prevent ground loops with other gear; works great.

Also, you should try mounting the toroid power transformer in an external enclosure. As I'm sure you're aware these Neve pre's are very sensitive beasties and having a big toroid radiating inside the box can cause disturbance. :grin:

Hope it all works out,

M.

 

[guavatone]

I was referring to the info on Joe's(JLM) post here:

http://www.groupdiy.com/index.php?topic=15373&postdays=0&postorder=asc&start=60
-scroll to the middle of the page. He explains how to hook up the grounds correctly.

 

[Greg]

Nice link !!!

So Adam, remove the 10R on both Hotrods and do not connect the Earth wire on either.

 

[bluezplaya]

I really do appreciate all the help in fixing this problem! :green: Okay let's see:

Is your JLM PSU (ACDC?) working properly when it's not hooked up to your pre? You're getting +24 and +48 right? Got those LM317's heatsinked properly?

Yes, it is getting 24+ and 48+ properly when not hooked up to the Neves. I don't know if the VRegs are heatsinked. How do I do that?

So Adam, remove the 10R on both Hotrods and do not connect the Earth wire on either.

I will do that. :green:

:guinness: :guinness: :guinness:

 

[bluezplaya]

WEEEEEEELLLLLLLL.......Okay. I wired up the star ground and pulled the Hot Rod board Earth and 10R out of the picture as per Joe on the previous post. I replaced the 2N3055 on both cards (it's a good thing I won a lot of 10 on Ebay :wink: ) but now the 10R on the PSU is glowing red :shock: . So I guess the next thing and only other thing left to do is bolt the voltage regulators to the case?! I think that's right? :roll:

Now I think something went haywire with the PSU.

Hang on a second....
:guinness: :guinness: :guinness: :guinness: :guinness: :guinness: :guinness: :guinness: :guinness: :guinness:
...(burp)....(buurp).....
okay, I feel a little better but the only problem is my **** still doesn't work

AAAAAAAAAAAAAHHHHHHH..........

:guinness: :guinness:
okay, I'll gather my thoughts