Citation V clone rebuild

[nerdorama]

I'm probably starting this thread prematurely since it will be a little while before I have results to share but I am a little too excited to wait. My Christmas present to myself was this amp from BT.

https://audiokarma.org/forums/index.php?threads/hk-citation-5-transformers.893602/#post-13306056

I've done a bunch of study so far, have received a set of output tubes from Jim McShane, and yesterday put in an order to Mouser. This amp needs a lot of rebuild to freshen it up for service. The circuit looks to be an exact copy of the Citation V and has original transformers. I've pondered whether I should strip it down and finish, or maybe replace, the chassis but I almost think I like the raw DIY look.

Thanks for listening. Any ideas, suggestions,comments welcome.

Happy New Year,
John

 

[crispycircuit]

Any pics?

 

[GordonW]

The Citation V was one of the very best implementations of the classic Mullard circuit I know of. Great choice of components in the driver stage- possibly the best pentode and dual-triode available for their respective purposes- though changing the 6CG7 to its functionally-identical- but-in-a-different-base-version- the 6SN7GTA/6SN7GTB= could give more options for finding the most optimal tube. It would require no circuit changes, other than the socket and tube...

It would be very interesting to take that, and add a few enhancements (EFB, maybe?), to see what it really can do. I'd think it could be really spectacular, with that iron...

Regards,
Gordon.

 

[nerdorama]

Post #4 of the thread I referenced above has a full set of pics.

 

[nerdorama]

My Mouser order came in on Monday and I'm home from my trip so getting a start. I have some 1200v Cree diodes and wonder if I might use singles of them instead of series pairs of UF type diodes. It would make this area of the pwr supply a little simpler and neater. Fishing for comments. Here's a not very interesting progress pic.

Thanks,
John

 

[GordonW]

Those diodes should be absolutely fine in the PS, one per leg of the power supply. No need to put them in series. .

It's a voltage doubler- which means each diode sees half the normal peak voltage that they would, if it were a standard full-wave supply. They only should be seeing about 500v across them- so 1200v is plenty of headroom.

Regards,
Gordon.

 

[nerdorama]

I figured but like to ask in case I missed some point. It will simplify the physical arrangement.

Now that I'm starting, I am feeling a bit excited about the project. I think I should replace the octal sockets as one is shedding a pin to the top side. Probably all the wiring should be new as well.
Thanks,
John

 

[quadaptor]

I'm probably starting this thread prematurely since it will be a little while before I have results to share but I am a little too excited to wait. My Christmas present to myself was this amp from BT.

https://audiokarma.org/forums/index.php?threads/hk-citation-5-transformers.893602/#post-13306056

I've done a bunch of study so far, have received a set of output tubes from Jim McShane, and yesterday put in an order to Mouser. This amp needs a lot of rebuild to freshen it up for service. The circuit looks to be an exact copy of the Citation V and has original transformers. I've pondered whether I should strip it down and finish, or maybe replace, the chassis but I almost think I like the raw DIY look.

Thanks for listening. Any ideas, suggestions,comments welcome.

Happy New Year,
John

The link isn't working

 

[nerdorama]

It works for me.

 

[RickB]

It works for me.

You have to be an AK subscriber to see it.

 

[nerdorama]

Sorry, it is in Barter Town. Wasn't thinking. Here are some pictures.

 

[Mike Stehr]

Here are some pictures.

Do you have any ideas what you'll do for the cosmetic appearance of the amp? I (think) you mentioned just a leave it alone kind of thing.
Me, myself would at least hit the transformers with another coat of brown. Are you going to retain the sticker labels?

 

[nerdorama]

Not sure yet.

 

[RickB]

Just because something is "homemade" doesn't mean it has to look that way...look at anything Luther Ward, Wardsweb, has made and see.

 

[nerdorama]

I understand RickB. But since it is already "built", not sure I want to completely disassemble it and rebuild. If I had just built it I wouldn't want it to look like this but since it was built years ago I don't mind the classic DIY appearance. It's put together pretty well, just not finished. If I ever do a complete disassembly, I will get a new chassis and snazz it up. Who knows, maybe in the course of the current scope of getting it running I'll be so close to a complete disassembly that I'll go ahead anyway and get a new chassis.
Thanks,
John

 

[RickB]

I understand RickB. But since it is already "built", not sure I want to completely disassemble it and rebuild. If I had just built it I wouldn't want it to look like this but since it was built years ago I don't mind the classic DIY appearance. It's put together pretty well, just not finished. If I ever do a complete disassembly, I will get a new chassis and snazz it up. Who knows, maybe in the course of the current scope of getting it running I'll be so close to a complete disassembly that I'll go ahead anyway and get a new chassis.
Thanks,
John

I totally understand, I have an Eico HF-89 in the same state...I've had it since the early '90's....a BIG undertaking, basically I would do a complete tear-down and follow the kit building instructions after painting the chassis and Xformers...

 

[Nyjblbob]

I totally understand, I have an Eico HF-89 in the same state...I've had it since the early '90's....a BIG undertaking, basically I would do a complete tear-down and follow the kit building instructions after painting the chassis and Xformers...

I agree with a total strip and at least a nice paint job.
Unless you get a real Cit5 Chassis it will never be a Citation 5!
Why not make it not only pleasing to look at,
But a better performance Citation 5 klone?
One you can use daily and say I made that and
It Performs better than a stock Citation .
Bobhorn
Btw my other Citation 5 is going in for a check up and a few mods. Along with the Triode switches I’m going to try a quad of the Russian
Nos military 6L6GC substitutes
Bobhorn

 

[RickB]

I recently bought a quad of the 6PS3S-E's and 6P3S's...I know the non-SE's aren't supposed to work for very long in the 240, but I bought some Pearl tube coolers for all the tubes, and put an IERC tube shield on the first 12AX7, and they have been plugging away just fine for months. I haven't tried the S-E's yet as the cheap ones have been sounding just fine and no problems...I also have a quad of TS 7581A's that are superb.

 

[Nyjblbob]

I recently bought a quad of the 6PS3S-E's and 6P3S's...I know the non-SE's aren't supposed to work for very long in the 240, but I bought some Pearl tube coolers for all the tubes, and put an IERC tube shield on the first 12AX7, and they have been plugging away just fine for months. I haven't tried the S-E's yet as the cheap ones have been sounding just fine and no problems...I also have a quad of TS 7581A's that are superb.

I’ve seen tube coolers but never used them.
What do they do for the sound quality?

 

[RickB]

I’ve seen tube coolers but never used them.
What do they do for the sound quality?

Well, the biggest thing is that they make tubes last longer...back in the fifties the JAN testing proved that reducing a tubes envelope temp had a great effect on increasing tube life, my Collins R-390/URR and R-390A/URR are just filled with tubes and were expected to be on duty 24/7/365, and the IERC tube shield were developed for just such instances.

I do not find any sound degradation with the Pearls installed, and if it ends up costing me a lot less for tube replacement, especially the NOS tubes in the front end of my MC240, or the replacement tubes for the Audible, then it's a good thing...

And no, I have nothing to do financially with Pearl, I'm just a very satisfied owner.

I am also observant of the fact that the entire amplifier runs cooler, whether it's my VTA-70i or the 240, and the room doesn't get as warm....it radiates the heat from the unit more efficiently before heating the entire unit up to higher temps...my digital IR thermometer confirms that the chassis even runs much cooler when the power and input tube temps are brought down...kind of like back in the day putting a better radiator in a hot rod along with an external oil cooler helped keep the engine cooler even in 100+ degree weather here in Texas....been there, done that.