Dumble 50W 3rd gen

[Nikk]

Hi all, my build is going well I powered up the other day and no smoke however I have a couple of issues.

I have no sound . but when I touch the meter between R21 or R22 and ground I get negative voltage -35volts, and and the speaker has sound .
I have another issue which may or may not be related If you cant tell I am no expert but have fixed amps and built a champ so I am not at ground zero. This issue is the capacitor C19 has 220 volts the one next to it C18 has 475 volts on standby.
I also seem to have low voltage at the filaments about 5.6 volts but I have not used the LED but a std jewel bulb tried removing this but no difference and the transformer is capable of 5A and I think i am around 3.2 so there should be no issue there . I know that there is a simple answer but I have reached my level of understanding on this one.
If anyone can help I would be very grateful .

Nikk

[Charlie Wilson]

First of all, the schematic appears to be for a #124 4th Gen. Skyliner. The -35vdc is your bias voltage. The 5.6 vac is too low.
CW

[Nikk]

Hi The Filament voltage is now sorted. I think my meter old is reading low new one bang on .

Sorry I attached the wrong Schematic .

[Nikk]

I appear to be getting 400V on pin 7of V1 just looking a diagram don't understand where this is coming from . I do now the ground is missing from r37 and c26 on the layout it is not marked on there. Let's hope it didn't fry the FET section .

[ijedouglas]

Hi Nikk,

It would be really helpful if you posted the schematic/layout that you are working from as well as gut shots of the amp you are working on. It is near impossible to help without this information.

[Nikk]

Hi there,

Can anyone tell me what is going on with the layout Vs the Schematic regarding the PAB/OD the layout has a DPDT for each where as the schematic shows a SPDT the Capacitors look to be in a strange arrangement on the layout also.
Can anyone tell me you do need the footswitch to operate this as the PAB seems to operate with no switch attached in mine yet I cant see how this is possible it is wired as per the layout . I have taken this out as I wanted to tidy it up a bit and get it right hence the question . I can see that the power from the regulator goes to pins 1 and 45 of the XLR switches through pins 2 and 4 supplying the relays PAB and OD . for the life of me I cant see how the PAB appeared to work with no footswitch connected .
The amp works although the Fet channel does not at present the sound is good and loud but it is obviously not 100% strange noises on the master and presence it is driving me mad as it all works fine to a point no smoke and 90% there just not quite . the trouble is I have reached my level of understanding nd it is the hard bit now finding the faults .I will keep going and check and double check until it works but any advise would be very greatly received . I also added an impendence selector switch as the transformer had 3 outputs and it seemed a good idea if I was to use another cab.
The speakers are 2x8" TF0818 celestions I was worried they would be thin but not at all the cab has a vented back in a wedge design this seems to work well . Made the cab and chassis trying to keep it as much as possible mine.

[ijedouglas]

Nikk,

As stated before, without any clue as to what layout/schematic you are using and pictures of what you are having issues with, it's very difficult to help. The folks on this forum are incredibly helpful and will be better equipped to help if they have some gut shots of areas you feel may have issues.

[donvan]

Can anyone tell me you do need the footswitch to operate this as the PAB seems to operate with no switch attached in mine yet I cant see how this is possible it is wired as per the layout . I have taken this out as I wanted to tidy it up a bit and get it right hence the question .

There is a PAB manual switch and a PAB foot switch. Your schematic only shows the manual switch. Based on your schematic, the circuit will work without a foot switch. Then manual switch puts the point that is labeled PAB on your schematic to ground in the OFF position.

[Nikk]

Hi Thanks for the post. I had it wired as per the Layout but it was working no idea why it was correct to the layout but is this actually correct. The capacitors are grounded on the PAB and the OD on the schematic which makes sense the layout however are not the same .

Dont pins 1+2 and 4+5 need to be connected on the XLR to power the relays?


Wish I knew more .

Nikk

[donvan]

I had it wired as per the Layout ...

I see where you posted the schematic you are using but I don't see anywhere in the any of your posts where you state which layout you are following?

[Nikk]

Did attach but may have not been included file size or something .

Attached now let me know if it is there.

Cheers Nikk

Untitled.tif

3rdGEN_50W_124_schem_AA_Electronics.png

Sorry trying to get the hang of these posts now they are there

[rootz]

Nope.......

[pompeiisneaks]

There should be an error message if it doesn't upload.

You could try posting to a new comment instead of the original thread? If not if it's say a PDF sometimes saving as a PNG or JPG will make it much smaller.

~Phil

[Nikk]

Getting Http error

What an arse that was hope it is clear enough as PDF.

Cheers Nikk

odss1.pdf

[pompeiisneaks]

I can see it but the resolution is a bit small and zooming in it gets a bit blurry so I can't read it, but my vision's getting worse and worse.

~Phil