I've made a start :) 50w #102

[norburybrook]

martin,

None of the switches work, I've got voltage going from 5 to 0 when I flick the switches so something's happening, but that's as far as it goes.



I've attached my relay wiring photos and checked them again. ( sorry about the burnt insulation, it's tight in there and they've now been in and out 3 times)

there's continuity along all the tracks back to their point of origin and from there back to the various points on the amp.

there also continuity from the rear toggle switches to ground when switching and back again from the -ve side of the diodes.

[martin manning]

Ok let's try this: measure ohms across the following pairs of points (at pot lugs or eyelets on the preamp board) with standby switch off (no DC on the tube plates):

With OD off:
OD in to Ground
MV 3 to clean out

With OD on:
OD in to clean out
MV 3 to OD out

With PAB off:
Bass3 to Treble 1
Bass3 to Bass cap
Bass3 to Bass 2

With PAB on:
Same as above.

[norburybrook]

thanks martin,

the time difference has got us I'm afraid, I'll do it first thing in the morning as I'm leaving the studio now.



Marcus

[norburybrook]

Ok let's try this: measure ohms across the following pairs of points (at pot lugs or eyelets on the preamp board) with standby switch off (no DC on the tube plates):

With OD off:
OD in to Ground 0.4 R
MV 3 to clean out 900k

With OD on:
OD in to clean out 900k
MV 3 to OD out 65k

With PAB off:
Bass3 to Treble 1 0.2 R
Bass3 to Bass cap 0.1 R
Bass3 to Bass 2 57k

With PAB on: all exactly the same
Same as above.

evening all, here's the resistance measurements Martin.


marcus

[martin manning]

The answers SHOULD be:

With OD off:
OD in to Ground 0R (you have 0.4R, check)
MV 3 to clean out 0R (you have 900k-something wrong here)

With OD on:
OD in to clean out 0R (you have 900k- something wrong here)
MV 3 to OD out 0R (you have 65k- something wrong here)

Looks like the OD relay is working but there is something wrong with the connections.

With PAB off:
Bass3 to Treble 1 0R (you have 0.2R, check)
Bass3 to Bass cap 0R (you have 0.1R, check)
Bass3 to Bass 2 0R (you have 57k, something wrong here)

With PAB on:
Bass3 to Treble 1 infinite (you have 0.2R, something wrong here)
Bass3 to Bass cap 0R (you have 0.1R, check)
Bass3 to Bass 2 infinite (you have 57k, something wrong here)

SInce you saw no change with PAB on/off it looks like the PAB relay isn't working.

Just to be sure we're speaking the same language, I'll see if I can mark up a layout with the test points to be used above.

[norburybrook]

Thanks Martin,

Tomorrow's another day

So close yet so far.

Marcus

[martin manning]

I went over the layout again, cleaned it up a bit more, added PCB traces, and some labels. The one posted above (all rock, no jazz) was not adjusted for the OD relay PCB you are using, which seems to match the Ceriatone layout.

[norburybrook]

Thanks Martin,

But I can't see any difference to the way I've got it wired at the moment.

I've been over this a couple of times with my breakfast this morning and if you compare the close up photos I posted they seem to tally with your layout.

What am I missing?


Marcus

[martin manning]

Hmm. I corrected my post above re your result measuring Bass 3 to Bass Cap, which should always be 0 ohms, and it is.

With OD off, you have 0R from OD in to ground (good), but you have 900k from Clean out to MV3, where these should be directly connected. Try measuring that on the relay PCB, where you should be measuring across a closed switch.

With OD on, Clean out to OD in should be a direct connection but you have 900k. Similarly, OD out should go directly to MV3. Try measuring these on the relay board as well.

[norburybrook]

Ok update and recheck.

OD off

MV3 to CL out is 0




OD on or off

MV 3 to OD out(pin 2 ratio) is giving around 1M




Marcus

[martin manning]

See if OD out is always grounded (OD on or off). You may have accidentally let the center conductor and shield come in contact.

[norburybrook]

nope, not grounded.

I'm still thinking I should be able to hear the relays switching though martin and I can hear nothing.

do you think 4.9v might be just low enough for it not to switch or do they have a largish tolerance?

MArcus

[martin manning]

They should pull in at 4.9 no problem. You have 5V at one coil terminal right? Try shorting the other coil terminal to ground (relay supply ground) and see if you can hear anything.

[norburybrook]

They should pull in at 4.9 no problem. You have 5V at one coil terminal right? Try shorting the other coil terminal to ground (relay supply ground) and see if you can hear anything.

yes I've got 5v coming in and when I flick the toggle switch the negative end toggles from 5 to 0


Marcus

[martin manning]

Ok good, now put your meter (ohms) across the each of the 22M resistors on the PAB relay and flip the PAB switch.