All things LA2a related

[Purusha]

Yap, the fuse was dead :thumb:

Will try to power it again tonight :grin: ...this time with correct wiring :green:

 

[CJ]

You might want to ohm out that first cap, I think it took a hit, which took the fuse out.

 

[Purusha]

I checked all four and most of the time I see around 20M. Only the second cap has around 300K resistance.

 

[CJ]

good deal.
self healing, ya know.

 

[Purusha]

The Hammond works Ok :thumb: Many thanks to Matta and CJ!

I connected everything and it looks fine. I see around 500VDC and 6.7V out of the Xformer. I powered the thing but with no tubes and no T4B. No smoke came out so far. :green: Is there anything I need to measure before installing the tubes and T4B. I think I checked all things a few times by now. :wink:

Oh, I quickly checked on 12AX7 #1 tube socket and pin 1 and 6 have 320VDC on... is this a good thing? I really can't check the rest as it's hard to come near the pins.

 

[dripelectronics]

hey there with no tubes or t4 , the 12ax7#1 voltage should be around 370 plus or minus
(im here in the states so i could blame my power company)
320 sounds good enough ,

im showing 388v before r29

and most of the tubes pin 6's read 380v

sound like the moment of truth :twisted:

g.

 

[Purusha]

OK, made some progress :thumb:

After I wired the heaters I powered up the unit. Everything looked fine so I set the meter scale to 0 in GR
mode and run some audio through. Sound goes through so this is a good sign but...

... the meter doesn't respond to audio in +4 or to gain red. in GR mode. Gain knob works fine but the GR
knob lowers the volume at last 15% when turning it CW. What could be the problem and where should I check first?

Is there any way to check my T4B if it works OK? Are there any other wires to be soldered under the PCB beside the heaters?

 

[drpat]

....

 

[dripelectronics]

http://driprecords.com/dripelectronics/pcb_manual1.pdf

 

[Purusha]

[quote author="drpat"]

This isn't a problem. The GR knob is supposed to reduce gain as you turn it clockwise, thereby lowering the volume. Check your wiring to the meter...[/quote]

know this :wink: but is it OK that I notice the GR so late at 80 on the scale of 100 and not before?

 

[Purusha]

I checked my meter wiring and it is wired OK so something else must cause the problem :?

Can someone tell me also what is the proper comp/lim wiring to the switch?

 

[dripelectronics]

http://www.driprecords.com/pcb/la2_hook_up_notes.pdf

a little essay on the pots/switch

g.

 

[Purusha]

Hi Gregory, I have all your PDF pots/switch notes :wink: but in the comp/lim notes there is nothing mentioned about when is either of these two engaged. For example when you short those two wires is LA-2A working as comp. or limiter?

 

[Purusha]

Hi Gregory, I have all your PDF pots/switch notes :wink: but in the comp/lim notes there is nothing mentioned about when is either of these two engaged. For example when you short those two wires is LA-2A working as comp. or limiter?

I will check again my wiring to be sure it's done 100% correct but other than that is there anything else I should check regarding my problems with meter? It shows 0 when in GR mode but it doesn't show either the output signal nor GR when I crank the GR knob fully CW. I hear signal going down at the max GR but don't hear any pumping effect so I doubt the GR really works as it should.

 

[matta]

Took me 2 seconds to work out by looking at the LA-2A schematic... maybe you should try doing the same instead of being spoonfed with every little thing, You are are taking the DIY out of DIY with all your projects :?

Cheers

Matt

 

[Purusha]

You are right, this one was easy :green:

 

[dripelectronics]

hi there ,

the meter section can be a bit of a problem ,

one of the common mistakes can be the meter switch it's self.
if it's an on -off - on with a midle position in the throw , those often don't
work.

the wireing is easy , but can be confussed .

your meter might need the diode rectifier configuration.

the most common mistake is a wire is loose, or the shield jacket
is shorting one of the pots .

check for solder or tiny wires shorting the pots or switches.

check your HAX GND make sure its soldered.

turn your stereo adjust pots / limiter response pots full clock wise or
full counter clock wise , one of those positions will bring on the juice.

g.

 

[Purusha]

your meter might need the diode rectifier configuration.

Thanks for the tips. BTW, I am using Sifam AL29. Don't know what meter you usually use in yours.

Will check everything what you mentioned twice and if I still can't get it fixed then you will hear from me again :wink:

 

[matta]

Purusha,

Your meter doesn't need a bridge rectifier, it is built into the Sifam. Happy troubleshooting, hope you get it all up and running, you are 90% of the way there already :thumb:

Cheers

Matt

 

[jho-audio]

Happy new year folks!

I'm using the drip boards and I need some help figuring out edcor wsm connections.. I have some loud hum and oscillation going on, likely more than incorrect transformer hookup but I want to get the in/out correct.

CJ style rendering of my current setup..

Is this okay?

Also, I'm using the edcor power transformer which has no ct on the heater secondary.. i will go buy some 100ohm 1 watt resistors to get reference to ground as im sure that this is creating some of my hum.

Cheers, Jason


EDIT: the xlr connections in the image are incorrect.. i have pin 1 to gnd and pin 3 is going to the transformers in place of pin 1. I am actually using 1/4" jacks and TR to transformer S to gnd.