Squeezed a 5e3 into a valve junior head.

[bakerlite]

Just waiting for the postman to arrive with my stuff from Doug and I can get cracking!


I have a valve junior (well " harley benton" same factory different badge) head that I have stripped out and hoping to get a 5e3 in there...


My immediate concern is space and especially  proximity to the OT of the preamp tubes -  do you think this will give issues?


bare in mind we are looking top down on the chassis (which is why Doug's board looks backwards!) so there is chassis AND turret board between us and the board components... hope that makes sense


the red area is unusable real estate due to fitting chassis into the cabinet.


would you guys do it different regarding the layout of the major top of chassis components?

[sluckey]

Don't put the OT near the little tubes.

I would drop the choke. Then rotate the OT 90° and move it next to the PT where the choke was. Then I would put all the tubes in a straight line that's lined up with where the 6V6s are now. Then move the board closer to the tubes to provide more clearance for the front panel pots, jacks, etc. If you just gotta have the choke, put it where the 5Y3 was located.

[bakerlite]

Thank you so much!


obviously my outputs and inputs and potentiometers are not on the top of the chassis but i have to show them just to be mindful of the fact they need space so you were right to suggest moving them. don't know what i was thinking making it unnecessarily tight.


the output jack holes are both drilled and labelled i think i can get a way with running the OT  secondary's straight up then turn right and run along the inner lip of the chassis to the jack sockets


As for the transformers i guess if the grain of the power transformer is at right angle to the output it should be ok that close?...

[bakerlite]

Hi - Got a few evenings done on the amp - i have a couple of questions..


1)is there a good link to how to wire up 3 output jacks so one is 4 . 8 and 16. I always get confused with output jack wiring / earthing.


2)i tried diodes on the rectifier socket but notice with them installed (the correct way i think) that of the 270v thats coming in on each HT lead  only 170v gets to the other end of the diode of both of them. why is this?

[sluckey]

1)is there a good link to how to wire up 3 output jacks so one is 4 . 8 and 16. I always get confused with output jack wiring / earthing.

Simply connect the 4Ω winding to the 4Ω jack, the 8Ω winding to the 8Ω jack, and the 16Ω winding to the 16Ω jack. DON'T USE SWITCHING JACKS! I like to connect a ground buss to all the sleeve lugs and also connect that buss to the power amp chassis ground.

2)i tried diodes on the rectifier socket but notice with them installed (the correct way i think) that of the 270v thats coming in on each HT lead  only 170v gets to the other end of the diode of both of them. why is this?

Sounds like you don't have any filter caps connected yet? I will assume the HT center tap is connected to chassis and one meter lead is connected to the junction of the diode cathodes and the other lead is connected to chassis?

[bakerlite]

he he  -well assumed - yes i was checking voltage at first stage of build where i had the PT wiring done and nothing else.


Its a tight squeeze and I dont want to have to retrace my steps - doh! so its normal - must refit the diodes.....




re the output jack sockets = is it that simple? i thought there was a voodoo to it? anyway, so  no GST jacks just regular tip and sleeve.... even I can manage that.


brilliant thanks

[sluckey]

re the output jack sockets = is it that simple?

Yes. Only use one jack at a time.

[bakerlite]

chugging along
i have never built anything this tight for space
hope it isnt hum central....

[HotBluePlates]

I'd say you're doing great! Getting everything to physically fit without an "Oops!" is the biggest challenge of the 5E3, even in a tweed chassis.

[bakerlite]

so got it all togeher.....
unfortunately i got a red plating 5y3 -- no other tubes installed .
5v heaters are fine - ht primary seems fine coming into the diode but only 170v after the diode - this is with no rectifier installed
i didnt get a chance to check with the rectifier in as i caught it quick....
can they last a brief (second ) red plate?
thanks


stumped

[bakerlite]

i have checked the wiring/board versus the schematic and it looks like I have everything in place.


The one  wrong thing I did do was leave a speaker plugged in when I powered it up with the rectifier in....... could that have caused it?


I thought the big no no was running the amp (when output tubes are in) with No speaker connected.

[sluckey]

There is a yellow wire with a ring lug connected to chassis at the same point as the PT red/yel and grn/yel center tap wires. Where is the other end of that yellow wire connected?

[bakerlite]

its the centre tap for 5v AC

[sluckey]

its the centre tap for 5v AC

That's bad! Clip that yellow wire off at the ring lug and tape the end. Connecting that center tap to ground will kill your 5Y3 and maybe even your PT. Not all center taps are supposed to be connected to chassis. This particular center tap has B+ voltage on it and was meant to connect to the B+ filter caps. But you don't need it for this amp.

[eleventeen]

Perhaps I am completely hallucinating, but it looks to me like the keyway for your 5Y3 faces opposite to those of your 6V6 tubes. It looks like you are feeding HV to pins 1 & 7, should be 2 & 8.  You have a green wire apparently pulling your raw rectified DC from pin 2, which is OK but we would rather not use green for the wire color there as green implies ground.


Anyway, without specifiying the exact way you appear to have miswired the 5Y3, it appears miswired. it appears to me like you've miswired the 5Y3 based upon the keyway being flipped around relative to the 6V6's.


If any tube can withstand a brief redplating episode, it would be a 5Y3. Very tough.


But if I am completely wrong, Sluckey has your answer.

[tubeswell]

What Steve said. The CT on the 5VAC winding is an alternative B+ connection, which can be used instead of running a wire from pin 8 to the reservoir cap (but otherwise should be clipped off and insulated). Even though it is the neutral part of a 5VAC cycle, it is meant to be one which is sitting at several hundred volts positive. Connecting it to the ground results in a high-tension short to ground, which is bad.

[sluckey]

Perhaps I am completely hallucinating, but it looks to me like the keyway for your 5Y3 faces opposite to those of your 6V6 tubes. It looks like you are feeding HV to pins 1 & 7, should be 2 & 8.

The 5Y3 key is pointing north in the pics. First pic is easier to see. Socket is wired correctly.

[bakerlite]

A sincere and heartfelt thankyou!   


She is up and running now that the CT of the 5V AC is discconected.  I must learn what i misinterpreted from that mistake as i did it intentionally thinking i was right based on what I understood the Datasheet for the 370fx to indicate so there's some basics there I need to get to grips with.


Anyway - it sounds Brown.... like dirty brown .... really good though :) I am not sure is it a tad too breakup inclined but I will have to play it some and see.


Also - it is incredibly quiet - like no hiss or hum AT ALL and i havent even put it in the cabinet yet which has some minor shielding. thats a great success considering how criss crossed it is!!


Pin 8 rectifier     276V
V1     Pin 1=   90V      Pin 3= 1.5V    Pin 6=84V  Pin 8=  1.4V
V2     Pin 1=   116V      Pin 3= 0.9V    Pin 6=146V  Pin 7=  12.5V  Pin 8=  33.1V
V3     Pin 3=   269V      Pin 4= 240V    Pin 8=14.5V 
V4     Pin 3=   269V      Pin 4= 240V    Pin 8=14.5V


Again,  Thankyou   

[sluckey]

I am not sure is it a tad too breakup inclined

I think you could benefit from increasing the B+. Try your SS diodes rather than a tube rectifier. How much B+ do you have now? Does it stay clean a little louder now?

My 5E3 runs happily with 340V B+.

[bakerlite]

good idea - of to gigs now so no tinkering for a few days.


I have 3Amps on my 5V rail - would other rectifiers be an option?

[sluckey]

I have 3Amps on my 5V rail - would other rectifiers be an option?

Yes. I only suggested the SS diodes because they will take the B+ as high as that PT will go. You can use a 5U4, 5AR4, 5R4, 5V4, etc. But if your 5Y3 is a current production tube, none of the other tubes will give you much more B+.

[bakerlite]

Just an update to say that I am really enjoying this little amp!
Still in the honeymoon phase and it gets a workout most days - To be honest I have never enjoyed a simple vol+tone amp as much - I have decided not to 'chase' the clean either -I have a 5v4 coming for it and after that it is what it is - besides the breakup is pretty spectacular sounding.
grin factor = 10
thanks again for the help

[alerich]

Also - it is incredibly quiet - like no hiss or hum AT ALL and i havent even put it in the cabinet yet which has some minor shielding. thats a great success considering how criss crossed it is!!

Excellent. I was waiting to see how the hum situation was. I crammed a Marshall JCM800 50W 2204 circuit into a Park G10 practice amp combo cabinet. Sounds great - I love it but there is a little bit of hum. It hums a little when the amp is on and running. I can ground the wiper of the master volume pot and it goes away but I haven't been able to track it down and it's not overbearing so I live with it. Everything is jam packed on top of everything else. The thing is that the amp hums a little even in standby with the power tubes removed. I'm getting some induction from the PT to the OT. There are oriented 90 degrees with respect to one another but they are right beside one another - a compromise I have to live with in the tight space.

Glad you are digging your amp! There is nothing more satisfying than cobbling together an amp from a pile of parts and have it sound great.