Andy40's Mojotone Tweed Deluxe build diary

[Marcel]

Progress update.....glaciers move faster than me....

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Yup, very nice work there Andy.
Remember to check everything, and when done check everything again....

[DrNomis_44]

@ Andy40 If you ever end up needing to order valves or new parts for your amp, there's a great company located in Australia called Evatco that you can order stuff online from rather than having to order from the US, here's a link to the Evatco website:

https://www.evatco.com.au/

[Andy40]

thanks doc. 'll post a pic of the completed chassis tomorrow. I'll be firing her up tomorrow arvo so if I blow anything, I'll be ordering aprts from these guys.

[DrNomis_44]

Seeing as Evatco do have 5E3 amp chassis in stock, I'm going to look at buying all the parts needed to build a 5E3 amp next year, would be cool to have one so I can take it to the Nirvana club just up the road for a jam.

[Simon Barden]

How do they suggest the initial firing up? I'd do it in stages. Start without any valves fitted, just in case there are some obvious shorts that take out the main fuse, then add the rectifier valve and test, then the pre-amp valves and test, then add the the power amp valves. (Don't forget to have the right impedance load connected).

Hopefully nothing goes wrong and you get a wonderful Deluxe sound.

[DrNomis_44]

First thing I would do after completing an amp build like this is to go have a good break to refresh, and then come back to it with a fresh mind, then I would check all the solder connections to make sure I hadn't made any mistakes, and then I would start doing all the test procedures prior to installing any of the valves.

[Andy40]

Thanks doc and Simon. It took me a lot longer than expected. Doc was right taking breaks and coming back to check. I did find the odd mistake that way.

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[Andy40]

Simon. They do recommend that you check the voltages in stages. Unfortunately and weirdly without the full load of all tubes and speaker plugged in I was getting some really high voltage readings.

Anyway maiden schwang worked great. It sounded a lot better than I thought it would.

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[DrNomis_44]

With just the rectifier valve plugged in (I'm assuming it's a 5Y3 valve), the voltages will be higher than normal because the power supply isn't being loaded-down by the other valves, once the rest of the valves are plugged in you'll find that the voltages will drop-down to about where they should be, the two 6V6 power valves will be drawing the most current from the power supply out of all the valves together, on the other hand if the voltages were higher than what they should be when all the valves are plugged-in that would indicate that something is wrong, but since the amp seems to be sounding good, then it looks like it's all working as it's supposed to, but a good idea is to check the voltages with all the valves plugged in and compare them to what the assembly manual says they should be, it's okay if the voltages are a little-bit higher with all the valves plugged-in, but not significantly higher.

[Andy40]

Yep you are right Doc.
Look the instructions require you to check certain voltages before you plug valves in.
Then check voltages after the rectifier (5Y3 - yes you are right) but as you pointed out it was heaps higher without any of the other valves plugged in.
Once the others and the speaker was plugged in the voltages were pretty good.

I muffed the Normal jacks somehow, I think I have a old solder joint there somewhere. I'm going to discharge the CAPS and fix it later or tomorrow when the wife's around.

A few questions for you doc:

I think I read somewhere that you have build some kind of bleeder that will bleed the caps to ground when you turn the amp off? or did I make that up?

I think i'm going to place an order for replacement valves from Evatco and another slow blow fuse, what brand of valves would you buy?
Its currently got JJ's in it