Anyone know a good place to buy VTL5c1 optos?

[Transcend]

I've got my SLO clone kinda finished but im having a bit of trouble with the switching.

So i was planning on replacing the optoelectronics as i may have whacked a bit too much heat on them.

I know i can get them from Mouser & Farnell but i don't want to spend £12 shipping on something that comes to less than that anyway

[Frank]

RS Online have them but it still looks pricey

Can't you cheat and use relays?

[Transcend]

Cheers frank

That is my next plan.

I just swapped out one of the LDRs that i thought was fried but still the same results.

I have one more thing to try thats been reccomended by a friend and then its onto planning relay layouts

[Frank]

Can't you test them with a battery and a series resistor to turn the LED on? Then check the resistance on the other terminals?

[JacksonRR]

What Frank said. What's the behavior right now anyways? Why are you looking to replace them, that is.

[Transcend]

the OD channel is fully switching in & the clean doesnt switch off at all.

And yes i've just done some testin and theyre all fine.

For the Clean channel

LDR 1 & 4 should be on about 1.8-2v

for the OD

LDR 3 & 4 should be on about 1.8-2v

this is what im getting

clean
1 = 1.94
2 = 0
3 =0
4= 1.94

OD
1 = 1.71
2=1.91
3= 1.91
4=1.72

I've double & triple checked all other components in the switching circuit.

It's really doing my head in that i can't get 1/4 to turn off

[Frank]

Schematic might help! If the LDRs are ok then it's probably just one wire out of place somewhere in the switching circuit.

Rip it all apart and start again?

[Transcend]

http://www.infocus.ho8.com/c3amps/schem/

The schematics and layouts are in there.

The switching part is in electrical 2.pdf

And yeah im considerin rippin it apart and starting again it's crossed my mind a few times

[Frank]

While you were posting I found the original Soldano schematic on my hard drive!

You're certain the LDR's are the right way round, 2 and 3 the opposite way to 1 and 4?

Maybe try replacing them with red LED's and see if they light up they way you expect?

[Transcend]

While you were posting I found the original Soldano schematic on my hard drive!

You're certain the LDR's are the right way round, 2 and 3 the opposite way to 1 and 4?

Maybe try replacing them with red LED's and see if they light up they way you expect?

The PCB i have has been made so 1 & 2 are the opposite way to 3 &4


Same layout as this exactly. I couldnt find a full size pic of the sloclone ones that i have.

I didnt think about trying LEDs,

I'll run down to maplins tomorrow after work and try that.

Cheers for the idea Frank

[Frank]

Definitely grounded to the chassis? Bridge rectifier connected up right?

What happens when you short the jack socket, same result?

Out of ideas here! And thinking about it, the LEDs won't tell you much. You already know the voltages aren't switching right, it'll just make it a bit easier to spot when it's working right.

[Transcend]

yeah its grounded to the chassis and when i short the jacket it does the half switching that i mentioned above

i originally had the wiring the wrong way to the jack tip/sleeve

when it was like this LDR 2 & 3 wouldnt function at all swapped them around and now im getting them all functioning just 1/4 wont turn off

And yeah the bridge is in correctly.

I get 5.9vdc out from memory

[JacksonRR]

Sounds like you need to dig in for awhile with a clear head and trace it all, looking for that one simple thing you overlooked. Are you sure they are in the correct orientation?

[Transcend]

yeah i'm sure they are in the correct orientation

I have attached some pics to show.

1&2 are reversed & 3 & 4 are face up.

i did some further tinkering today. I removed the 15r resistor in the switching circuit and jumpered the pads.

This got the LDRs 1 & 4 down to 1.2v which is a good improvement i think if it change a few values i could get them to drop down to about .7v which is where i need them to be.

once i have done that i will possibly do the LDR5 mod to completely get rid of the channel bleed.

but for now i have removed the LDRs and jumpered the OD positions as thats the main thing i wanted this amp for and im gonna actually have fun with it rather than stressing and then do a rewire @ the weekend and clean off any flux that there may be under the board & reheat all the connections & also change the BR even though i think its fine.

Thanks for your help guys i shall keep you posted

[Transcend]

got it sorted. It was a retard mistake.

But now that this issue is sorted i'm really proud!

First amplifier build ever and its one that i got told i would never do without massive amounts of noise & oscillation and i have neither!