Paoli Model 60M help

[theurbanshaman]

Got a pair of these Dynaco Mk IIIs on steroids on Ebay after hearing about their great reputation. They sound sweet using the 8 ohm taps with 8 ohm speakers! The only problem is my preferred speakers are rated at 4 ohms; there is only a trickle of sound using the 4 ohm taps, and the sound of the speakers are way off if I use the 8 ohm taps with them. The only local repairman who will look at tubes swore that there couldn't be 4 ohm taps on a Dynaco amp, so I crossed him off the list.

It seems that someone in the past replaced the binding posts and may have tampered with the wiring in the process. I'm just trying to find out if anyone might glance at my photos and see if they can give me a clue about why the 4 ohm tap might not work on either channel.

Thanks!

https://drive.google.com/file/d/0BxGqB8rQeVOfMzFSTVg4TWVoZW8/view?usp=sharing

https://drive.google.com/file/d/0BxGqB8rQeVOfSGRRM21pQnJDVUE/view?usp=sharing

 

[Altecboy]

some things to check

Is this on one amp or both? If its on one, I'd reflow the solder connection at the binding post. On that amp, the brown lead is 4 ohms. the orange is 8 and the yellow is 16. So it appears that the lower tap is 4 ohms.

I would disconnect the speaker and put an ohm meter from the 4 ohm tap to ground and see if you have a continuity or, perhaps, a broken wire from the output transformer to the post.

If you want someone else to take this on, contact Joe Curcio over at Curcio Audio. He worked on the design of that amp when he was with Paoli.

Good luck.

 

[Salectric]

It's true the Dyna Mk. II did not have a 4 ohm tap, only 8 and 16. However, your amps must have started life as a Mk. III based on the photo of the rear panel since it clearly shows 4, 8 and 16 ohm outputs.

 

[petertub]

Pauli was a rebuilt MkIII

If you mount the original speaker connector then 4 8 and 16 ohm taps are acceccible.
The transformer secondaries is :
Black = common
Brown = 4ohm
Orange = 8 ohm
Yello = 16 Ohm.

BUT : i have no pauli schematic at hand, possibly they intemixed the secondary in a simular way as
audio research has done, consult pauli schematics to confirm secondary winding usage.

Schematic found, if it's correct there is no changes in secondary connections.
http://www.blackdahlia.com/html/tip_84.html

 

[CarlyBoy]

Ahh, the Paoli 60Ms. Another couple of pieces of gear I should not have let go. I console myself with the fact they found a good home with a friend. Nice link there with some good historical info.

 

[theurbanshaman]

Is this on one amp or both? If its on one, I'd reflow the solder connection at the binding post. On that amp, the brown lead is 4 ohms. the orange is 8 and the yellow is 16. So it appears that the lower tap is 4 ohms.

I would disconnect the speaker and put an ohm meter from the 4 ohm tap to ground and see if you have a continuity or, perhaps, a broken wire from the output transformer to the post.

If you want someone else to take this on, contact Joe Curcio over at Curcio Audio. He worked on the design of that amp when he was with Paoli.

Good luck.

The crazy think is that it's the same on both amps! I did contact Joe Curcio and I think my best bet would be to send them to him and possibly add some of his mods, but to start with that's a minimum of $100/per amp plus the price of shipping the two amps both ways. Was trying to see if there was an easy out for now.

 

[theurbanshaman]

It's true the Dyna Mk. II did not have a 4 ohm tap, only 8 and 16. However, your amps must have started life as a Mk. III based on the photo of the rear panel since it clearly shows 4, 8 and 16 ohm outputs.

Yes these definitely started as MK IIIs

 

[Salectric]

I can't swear this is correct, but I am fairly sure the original prototypes of what became the Paoli 60M were built on Mk. II amps, not Mk. III. I heard them at the home of the designer Walter Key back in the early 1970s. This was before Key hooked up with Gene Coggins at Paoli HiFi. Of course, it doesn't really matter which amp chassis was used as a starting point. After the mods, the only real difference would be the lack of a 4 ohm tap.

 

[petertub]

I can't swear this is correct, but I am fairly sure the original prototypes of what became the Paoli 60M were built on Mk. II amps, not Mk. III. I heard them at the home of the designer Walter Key back in the early 1970s. This was before Key hooked up with Gene Coggins at Paoli HiFi. Of course, it doesn't really matter which amp chassis was used as a starting point. After the mods, the only real difference would be the lack of a 4 ohm tap.

The lack of 4 ohm outlet was not a fact of changed transformer, it was a fact of mounting less that enough output posts. Change output posts and reconnect the
missing (brown) lead and you are back in game.

I never understand why folks wants banana plugs for speakers,

 

[theurbanshaman]

Hey guys, I got my speaker posts issue on my Paoli Mk 3s worked out from a nearly two years ago. Now I'm trying to switch over to 6550B tubes instead of the installed 8417 output tubes. There are separate adjustments for each power tube - bias on the 8417s was set at 40ma, but the 6550s don't like that. Lowered it to 30ma but I'm suspicious at the hot smell. Reading online posts, I've seen bias values range from 30 to 70. Anyone had experience with 6550s on the Paoli Mark 3s?

 

[Eli Duttman]

The 6550B was superseded by the 6550C. Very sadly, the St. Petersburg, Russia, plant that made those tubes is defunct. Be extremely cautious about buying any of the remaining stock of those tubes, as they rate to be problematic from both a performance and cost perspective.

A stock Dyna MK3 runs just fine with KT88s. The "reissue" Gold Lion (GL) KT88 is excellent. The overall quite decent ElectroHarmonix (EH) KT88 is less costly than the GL, but comes up a tad shy in the bass extension dept.

 

[theurbanshaman]

Thanks, Eli, for the heads-up regarding 6550B tubes. The NOS pairs I purchased about a year ago were rebranded with the "Billington Gold" label and had test values penciled in on the box. I do have a quad of EH 6550s that I could swap out from another amp to try. Then there is still the question of bias setting for 6550s in the Dyna Mk III/Paoli 60M.

 

[skidave]

What was the resolution to the original 4 ohm output problem?

 

[theurbanshaman]

Truth be told, skidave, I shelved the amps for a while, brought them back out to use with 8 ohm speakers, and when I tried the 4 ohm output it magically was working!

 

[crispycircuit]

A christmas gift?