Build start- grounding Q

[The Captain]

Ah ok, this idea seems a good one and of course if Bruce says so too.. when you say the 'back' of pots, is that literally? or just connecting gnd lugs of each pot together.. surely the wire has to run to the chassis somewhere too?

I certainly am not trying a more clever approach, or reinventing- lordy no! Basically unless the tweed chassis ordered has a brass plate (no in my case), Im gonna have to choose a gnd scheme & oddly there isn't a clear ref pic or layout that showing exactly what could go where on the net with any system.

Cheers, Capt.

[The Captain]

Does anyone know how I figure if I have a matched pair of 6V6 GT's? there are no markings on box- I presumed ordering 2 EH's with ~$300 worth of 5E3 bits that at least I'd be told if they were not usuable: all TAD have replied is.. 'no they are not matched'.

Cheers Captain.

[MWJB]

Yes, solder the buss wire directly to the back of the pot body, remove any varnish that might impede the soldering process. The wire runs from the pots terminating at the ground lug of the #1 input jack.

Ask TAD to replace the non-matched 6V6s with a matched pair.

[stokes]

If the supplier tells you they are not matched,then that is your answer.To see if they are close enough for your purposes you would have to put them in an amp and check the current draw of each,if they are within 5ma's they will be fine,otherwise return them and ask for a matched pair.If you are just starting this build,you are in no rush for the power tubes,I would just return them and get a matched pair.

[The Captain]

Thanks again. I dont think much of TAD; wrong bits, ages replying to emails and abrupt- I get feeling they won't replace these valves either..

That grounding seems simple and I guess uses the pot's casings for '3 gnd refs'- am I right here tho: with plastic jacks (no metal parts to chassis) this copper wire still terminates at one of the four jack gnd lugs ie. the copper wire is 'suspensed' without an end to the chassis?

muchos gratias, Capt.

[The Captain]

Well the build is going well- waaay more fiddly than expected (there ain't much room in a 5e3 chassis thats for sure!). Near complete with a matched pair of 6v6s coming soonish; I have though come to a puzzling halt-

Im trying to figure the 'top' (on layouts) pair if input sockets, noticing they have a 3rd lug ('switch') leading to their next inputs: I've got these placcy inputs with 2 pairs of lugs, one pair tip t'other sleeve (contact breaks once jack inserted). How would I wire these up as per std layout?

Thanks, Captain.

[MWJB]

In the absence of grounded metal jacks and assuming that you don't want to drill a hole in your new chassis, I'd run some stranded wire from the buss wire at the Normal 1 jack to a ring terminal and trap it under the nearest chassis bolt nut, unless you can find a ring terminal big enough to fit over the Normal 1 jack?

[sportster4eva]

Captain~
Thinking about your grounding question, and not having the brass plate, I had an idea that you may wish to entertain. Looking at the eyelet board with the filter caps to the left, you could possibly use a section of solid 18-20 gauge wire and go from the eyelet where V1's cathodes are supposed to go to ground (first eyelet) and go up and over to the next cathode's ground (8th eyelet) then to the third filter cap, then to a power trans bolt. It would only have to extend far enough above the board to clear the other eyelets and not touch the input jacks. Then the input jack grounds and the volume pot grounds could go to this little "Buss", and should be quiet. Wish I had done mine this way....the brass plate was a pain.. You cant solder to it if it's in the chassis.. too much of a heat sink.

[The Captain]

Thats an idea MJWB- I thought one end of the copper wire should go to a chassis bolt somewhere with these pesky placcy jacks. So far Ive got:

Mains lead gnd to bttmL PT bolt.
Both PT centre taps to topR PT bolt.
Input 1/ wire end & spkr jack gnd to bttmR PT bolt.
Along the copper wire from L to R: 25uf/ 270R 5w (topL from board to beginning of wire), then gnd from pot 2 (cap from 1st pots gnd lug joins here), then 3rd 16uf filtercap from board, gnd from pot 3, wire snakes to all input jacks gnds with last board gnd (topR from board) going to the wire between normal input 1& 2.

If anyone can spot a blunder before I get the solder out, Id be grateful for a shout. Thanks Capt.

[stokes]

"Input 1/ wire end & spkr jack gnds to bttmR PT bolt."Your input ground is a "low current",your speaker jack ground is high current,they should not be together,also you have your power tube cathode components(25uf/270R) with that"gnd from pot 2).To make it simple,consider this.Your high current grounds are the main and screen filter caps,your power tube cathode components,speaker ground or OT ground,heater supply center tap or the 100ohm "artificial CT" for the heaters and your PT CT.These should all be grounded together on one of your PT bolts,and not with any of the preamp or input or vol & tone pots.All the other grounds are low current and should be grounded at the other end of the chassis.Whether you use the back of the pots or a seperate ground lug near the inputs,they should be kept away from the "high current" components grounds.I use terminal strips which have a ground lug on each end and ground all the preamp,input,and pot grounds on these.You could also drill a small hole or two and put a ground lug at the end of the chassis away from the PT.Grounding the low current components and the high current components near or together with each other may introduce high current in the preamp components and introduce hum,which gets amplified with the signal.Regardless of what they are grounded to,a brass plate or the back of the pots or even just a glob of solder directly on the chassis,you need to keep the high and low current components grounds as far from each other as possible.

[The Captain]

Ah.. good job I asked 1st! This is really confusing, as many have offered different ideas and net pics differ or are not clear enough..

So revised gnds:

Mains lead earth to bttmL Pt bolt.
* 2x PT centre taps, 25uf/ 270R gnd from board, 3rd 16uf filter cap gnd from board & spkr jack gnd ALL to topR PT bolt.
* pots, 2x gnds from (2x 25uf/ xyzRs) board, & input jacks to copper wire, terminating from last input to a new bolt nr inputs smwhere.

Is that the idea? thanks Capt.

[The Captain]

Thanks for the detailed help folks, alas I just cannot find my page telling me what pin is the screen/filter/cathode/grid etc so Im totally flummoxed now.. Im going to have to simplify my Q to-

I have 4 gnds from 'top' of board. If I were for simplicity's sake, to label them as:
1. 25uf/ 270R 5w
2. 16uf cap
3. 25uf/ 1.5k
4. 25uf/ 820R

I have 2 gnd points:
A. a PT bolt
B. a copper wire for pots and input jacks.

Can anyone help and tell me what nos. would go to A and B? thanks, Capt.

[stokes]

I dont know which 16uf cap you are refering to but the one connected to the preamp should be grounded with what I am refering to as low current components,the other two are connected to the CT of your OT and pin 4 of the output tubes.Numbers 3&4 on your list go to point B.# 1 goes to pt.A.I tried to simplify things in my last post,but I have to tell you,you should learn which pins are which.This is basic stuff. http://www.ampwares.com/ffg/index.html this is a link to a site with the schematic and a layout diagram for the "Narrow Panel Deluxe,which is the 5E3.You will notice on the layout that it shows the filter cap for the screens grounded with the cap for the preamp,this is considered "wrong" and should rather be tied to the ground for the main filter cap.It is a common "fix" for a 5E3 with hum problems and is a normal mod for these amps when restoring them.

[The Captain]

Great thats 1 to A and 3,4 to B. Thanks Mr. Stokes. As I said Ive lost (immensely irritating) where my pin info is for the mo and yes its basic stuff, so I tried to make my Q basic suffice to say..

The 16uf gnd Im referring to is usually the third of three identical 16uf/450vs. In this example it is a black 15uf; specifically it is the 2nd of 4 thick gnd wires from the top of this board- I don't know whether to terminate this gnd to a common PT bolt, or with the pots/ jacks/ 3rd/ 4th thick gnds pot wire-- can anyone help?: http://www.kilback.net/homebrewtweak...ircuitcard.jpg

I'd be immensely grateful- its the only thing left to do! God I wish Id bought a bloomin brass plate to whack the lot on..
Cheers a bunch, Capt.

[stokes]

That one is the preamp cap and gets grounded to "B".Like I said before a brass plate is not a necessity,the important thing is to have the grounds seperated as described to avoid inducing hum from higher current components being grounded with the preamp grounds,they dont even have to be all in one spot,as long as they are relatively far from the so called "high current" components grounds.I have often just used a glob of solder directly on the chassis at opposite ends of the chassis to do this.