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Excelsior modification

Sorry I was going to reply -looked at the time and realised I should have been on the road . So first thank you so much for your time -you don’t know how much I’m grateful . I understand the 2nd part of your answer and when I measured the voltage at the preamp valves there was roughly 6.2 volts . I’m not following the 1st part however due to my lack of expertise . So after the 6.3 passes through the resistors it goes to pin 8 of the 6FQ7 ? So the 6FQ7 heaters are not connected to 6.3 or am I misunderstanding . Are you an excelsior owner ?

No I'm not an owner. I'm a designer and repairer of amps etc and the "Jez" mentioned above.

I can only really comment on what is in the diagram.... my crystal ball for checking out yours from here and seeing whats different is a bit dodgy these days:rolleyes:

According to the diagram; V1 has it's own heater supply of 6.3V AC which is floated at HT voltage. The cathodes are at HT level and this would put strain on heater/cathode insulation otherwise. ie the heaters here run from 6.3V AC BUT the whole shebang is floated at say 250V DC above ground. V1 is not a regulator or anything like that but is wired simply as a pair of diodes in series... some voltage will be dropped across these but otherwise I can see no purpose to V1 other than to prevent HT being applied to the rest of the amp until V1 warms up.

All other valves have heaters supplied from 12V DC from the regulated supply. A half wave voltage doubler takes 6.3V from the transformer and doubles it... in fact there should be about 16V ish on the smoothing caps. It then goes through a 3 pin voltage regulator to give 12V. Valves such as ECC81/82/83 have centre tapped heaters and can be run from 12.6V applied to pins 4 and 5 or 4 and 5 can be connected together and 6.3V applied between there and pin 9. If you have the rest of the schematics for the whole unit it would be useful!

The regulator circuitry for the heaters will be bloody obvious if present and correct as apart from the 12V 2A regulator on a heatsink there will be 4 large 10,000uF electrolytics!

I'm rather busy and generally turning down work ATM but this is interesting enough and not to long a job so I could fit it in as a quicky if need be.
 
The 6.3v output from the transformer that supplies the separately boxed preamp is working fine . As you say I have around 17v prior to the regulator and 12.8 coming out of it and around 6.1v at the heaters on each valve in the pre-amp .
I will try to load the other circuit later after the relations have disappeared. I will also send a photo of the power supply showing what’s connected and what isn’t . And thanks for the offer -it’s good to know that if I cannot do it there is someone around who knows valve circuitry. I’m sure that it’s virtually a matter of a couple of wires to get it as the manufacturer designed. At one time I had 2 of these and how I wish I still had the other to guide me .
 
The 6.3v output from the transformer that supplies the separately boxed preamp is working fine . As you say I have around 17v prior to the regulator and 12.8 coming out of it and around 6.1v at the heaters on each valve in the pre-amp .
I will try to load the other circuit later after the relations have disappeared. I will also send a photo of the power supply showing what’s connected and what isn’t . And thanks for the offer -it’s good to know that if I cannot do it there is someone around who knows valve circuitry. I’m sure that it’s virtually a matter of a couple of wires to get it as the manufacturer designed. At one time I had 2 of these and how I wish I still had the other to guide me .
 
Ok , I get it now. Takes time when you are in your 70s ! I run the 6.3 output from the transformer directly to the heater of the valve and take a 100ohm resistor from pin4 and pin 5 to pin8 . So my only question is what wattage should the 100 ohm resistors be . Everything else on the board ties in with the circuit diagram .
 
Ok , I get it now. Takes time when you are in your 70s ! I run the 6.3 output from the transformer directly to the heater of the valve and take a 100ohm resistor from pin4 and pin 5 to pin8 . So my only question is what wattage should the 100 ohm resistors be . Everything else on the board ties in with the circuit diagram .

1W will be more than good enough. Be certain that it is as the diagram in that there is definitely a completely separate 6.3V winding on the transformer for JUST V1
 
1W will be more than good enough. Be certain that it is as the diagram in that there is definitely a completely separate 6.3V winding on the transformer for JUST V1
Yes the 2nd set of 6.3 windings are unused which is strange but for some reason on my box it was decided to control the HT by solid state even though the board is the one that conforms to the circuit I posted -strange -I thought at 1st that the 6.3 output was probably not working but it is . Anyway thanks again . I will get some resistors -wire up and hopefully all will be fine ‍
 
EH??? Both windings should be used! You know where I am if it blows up....
Yes I do realise that. I think I understand it now . I must admit I couldn’t understand why the circuit was suggesting those 2 resistors should go to pin 8 HT but you’ve explained it to me and it’s also mentioned on the TNT website on the excelsior page . Anyway nothing to lose as I nearly ditched it last week . I was going to use my transistor pre to drive my Williams Hart monblocs. I’m in no doubt there are a few on PFM who will have a good laugh if I have to come back to you with a burnt out pre. I did look to see if you are local to me and if you had been within 20 miles or so I would have brought it over -but I’m in Wolves and I think you are up Sunderland way . Anyway thanks I really do appreciate your help.
 
Jez -ok so after doing some decorating I’ve found time to change the circuit to include the valve as per the circuit diagram . I haven’t finished connecting some of the wires to the switch , light etc as I wanted to check voltages first . So the heater voltage to the preamp are fine . The Ht out is measuring 360v with no load . On the circuit diagram it is showing 270v I guess under load . What do you think ?
 
Whilst I have everything open I was contemplating replacing the cheap looking 2 pole 6way switch for choosing phono cd tuner etc . Has anyone a suggestion on something I can use which would be superior .
 
Yes that switch will do nicely . Thanks
Took the plunge and connected the preamp -all is working fine . Voyage dropped to 270 as per the circuit diagram . So thanks to Jez for rescuing this from going to the tip . It’s now running as per Doug’s final circuit diagram and all I need now is to update the selector switches as a priority. There are some good people around THANKS
 
Yes - very similar -I have 4 black caps for the heater supply . 2 black ones 220uf on HT and I did have one 100uf for the power mosfet which may have been a Glen Croft mod rather than a Doug mod . So glad I have Doug’s circuit diagrams of his Excelsior and Exquisite amps so that Jez could confirm how to wire the heater supply. Haven’t got a clue which is the better design Doug’s with a 6FQ7 or Glen’ without it . I have been without it for to long to compare. It really threw me when I opened it it up and there was no valve . Never had the lid off it since I bought it . I thought it was me in my old age . So this guy has taken Doug’s power supply and added his own pre design . I wonder if he’s been able to compare both.
 
Yes will do -I’ve put them in the loft but will get them out when next up there and send them . I met up with the guy who drew them up for him well after Doug died and he said he would get them out for me and post them . To my surprise he sent on sheets around 30x20 in’s. They are supposed to be the last design change . He had all of Doug’s designs . I should have asked him for all but didn’t realise then how valuable they would be to others .
 


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