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soundguy

Well-known member
Joined
Jun 4, 2004
Messages
2,041
Location
NYC, USA
hey fokls, my project for today is replacing the dead power transformer I have in an old rev d. 1176. I have a new avel lindberg torroid (model Y236107) to install and am not too sure how to do it. Has anyone ever installed one of these?

the transformer is marked as follows:

primary 2x115V
blue and grey
violet and brown

seconday
black (Ov) and red ((30V)
orange (0V) and yellow (30v)

the old 1176 has three wires on the secondary going to the rectifiers on the board. Im guessing I should be only using one half of the secondary, right? I should only be using one half of the primary for 110 operation or both together for 250, right?

thanks

dave
 
I just peeked at the schemo real quick(lookin at the UREI schemo), and it looks like it's using both parts of the secondary.

If you've got another original 1176 around, I'd measure it to see what it's puttin out.

How this would translate to the traffo you have is that the 0V would be connected and used as your 0V reference, so red and orange get connected from your new transformer.

you then use balck as one of your feeds (one of the red wires on the original schemo), and yellow as one of the other original red feeds.



The power supply is generating +30V DC, and -10V DC, with reference to ground, so I think it really does want both halves of the secondary.

The question for someone with more brains than I is whether the traffo you got has too much juice for the circuit, or whether it's fine (was the original traffo 30-0-30, or something smaller??)

That's my stab at it.

Regards

ju
 
Hi Dave,

Here's the Avel Lindberg colours related to the 1176 wiring:

Daves_1176_toroid.gif


This is a handy page:

http://avellindberg.com/transformers/y23_range_connections.htm

30V ac post-rectifier will get you ~45V DC, but bear in mind that this value will be lower due to the load of the lamps and circuit. The -10V is taken care of by the 2x 1k resistors and zener.

:thumb:

Mark
 
thanks mark!!!!!

can I get away with 45v? Im not running lamps in this box. that seems like it may be a little high...

dave
 
cool, I'll post a photo when I get it all together, Im actually totally repacking this old 1176 and rebuilding the whole board, stuff a bunch of holco resistors and black gate caps today. See what I can turn this thing into... Transferring everything to a par metal box and have this cool old simpson meter for it, should be completely stupid looking when I get it done.

I havent experimented yet but if anyone knows- can I just use a regular pot without a switch for the attack control and simply lose all the wiring from the switch portion of it and just have it in ON mode always, or does that need to be compensated somehow? would make life a lot easier than trying to find that part, the old one is dead.

dave
 
I also have an avel y236106 which has dual 26V secondary. Its labeled as a 30V transformer though. Would I be better off using this one, or am I splitting hairs?

dave
 
Hi Dave,

Cool project! Definitely post pics...

Yea, to reduce dissipation of the unwanted voltage as heat, use the transformer that has a lower no-load output. It's good that you're replacing components too- the +Ve supply smoothing cap (1000u) is usually rated 50V or so- not much margin for mains supply variation with a post-rectifier voltage of 45V or so. Replace with a 63V unit.

The switch on the attack knob can be removed, but just make sure that you make the connection permanent from the Ratio switchbank to the GR control amp. In the Compressor-Off position, it just disconnects the GR-amp input from the audio signal, and connects it to 0V so no signal will affect the GR. You can always replace it with a SPDT switch, or a DPDT switch, using the spare pole to switch a nice big "Compressor ON" LED/Lamp. If you need details on the wiring, let me know, and I'll refer you to the diagrams.

Mark
 
hi mark, yes, I already increased those caps.

if you have something drawn out, I would love to look at it, certainly would make things easier. So far the only thing Ive traced with the switch on/off is the connection to the two caps on the lower right hand side of the board. I havent even compared it to the schem yet, havent gotten into sersious testing with it yet.

dave
 
Ive spent some time tonight drawing out the ratio switch banks and meter selector switch banks. Is there anything that switch bank is doing that I cant do with individual dpdt's? Looking at the diagrams I have, I think a regular dpdt should work just fine. I need to spend some time on the other half, the power switch is simple, Id like to remove the +8 setting all together and just use the +4/GR on one toggle, Im working my way on trying to figure this one out. I dont know why I get so confused with switches but it sure frustrates the hell out of me sometimes...

dave
 
ok so pretty much the switching on this thing is the grand canyon and my retardedness is the colorado river...

Id like to eliminate the +8 switch (has anyone ever had occasion to use this?) put the power on a switch (easy enough) and then put the +4 and GR on one switch. Can someone check my head on this-

Im thinking this-

two leads from meter to center section of a DPDT switch.

two leads from PCB to +4 switch to outer section of DPDT.

two leads from pcb to GR switch to opposite outer section of DPDT.

This seems logical enough, however looking at how the multi switch is wired Im not sure it will work and I cant understand WTF is going on with that multi switch thing. Can anyone help me understand how the +4/+8 metering is derived?

It looks like I need to use the blue lead which taps the bottom of the output transformer on one side and then the red lead which taps the top of the OT and then through the 3.6K resistor for +4? I guess the +8 is just derived from splitting that and adding more resistance?

I think I just answered my own question, but can someone double check me? No harm should come by leaving the +8 tap from the PCB unloaded, right?

dave
 
Dave,

The wiring you stated there is correct. Here's the original:

1176_meterswitch.jpg


...and what you've got:

1176_meterswitch_DPDT.jpg


The +4/+8 is just switching in the 3k6 or 8k2 resistor on-board. Just leave the +8 terminal disconnected.

:thumb:

Mark
 
Hi mark-

thanks so much for the feedback, I think I got it wired right. I hammered it out yesterday and its coming along really well. I also wennt ahead and put the "limiter in" on a spdt instead of going with the attack knob switching arrangement or leaving it out all together. This allowed me to use a better feeling pot, and I put the limiter in switch right below the meter select which is a much more logical place IMO. Im hoping to finish the wiring to the board this week and test it out, I'll post some pictures, so far it looks really nice, Im glad I took the time to put this project together.

dave
 
ok, got the box together. have some problems, woohoo.

meter's dead, no audio. No -10V DC. Power transformer AC voltages look good. Figure I need to start with the -10v first. How does that get rectified? Should I be looking for a bad diode? Is there a way to test for a bad diode in circuit or do I need to desolder the component to check?

thanks

dave
 
Look at the circuit around the 10V Zener. Check orientation and such..

Not a complicated circuit at all

The meter won't work untill -10V is restored

Jakob E.
 
do these power transformer voltages look right to you guys? I have two amvecos wired as follows:

avel 236106
primary 110V
brown/grey neutral
blue/violet load

secondary
red/orange 90 V AC
black 116 V AC
yellow 63 V AC
avel 236107
primary 110V
brown/grey neutral
blue/violet load

secondary
red/orange 76 V AC
black 106 V AC
yellow 46 V AC


I measured the secondaries in my other 1176's and get 36V/36V/0V. Im thinking I either have the torroid wired wrong or its the wrong part. Any insight as to whats going on here?

the transformer secondary is black 0V red 25V and Orange 0V yellow 25V. Wouldnt it make more sense to connect black and orange for 0V (red/yel on the schematic) and then use the red and yellow 25V taps? I dont have the greatest understanding of power transformers so figured Id ask first, but as wired above, something isnt kosher.

dave
 
unloaded I get the following-

red 60V AC
yel 60V AC
orange/black 90V AC

This seems to make a lot more sense. Im still not understanding how 90V is going to work as 0V?

dave
 
omg this is pissing me off.

Ive tried it hooked up both ways and cant get a DC voltage in the circuit, the diodes test ok. WTF?

dave
 
ok, I took the PT out of a working 1176 and hooked it up and Ive got bigger problems. I need to pause to say the F word...

Diodes all appear to test good. All the power supply caps are in the right way. There's like 6 parts in the power supply. Any suggestions on where to start looking. I wish I could afford the amount of time Im putting into this, fuck another whole day wasted.

dave
 

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