CTS, Stancor, Chicago Standard Transformer model P-8164 info

[Toppscore]

Trying to verify the Chicago Standard Transformer 8164,
it's production years, it's performance specs,
if it is supposed to be in a vintage Fender amp, etc.
Decided to give the amp a Sprague Atom filter capacitor job.
I'll get the wattage specs and compare,
but four months ago I had the specs checked as the following:
Secondary: 640 VAC
Rectifier heater: 6.7VAC
Heaters: 5.1VAC
B+: VA 395vdc, VS 394vdc
Output power: ~40W
Miscellaneous: 20ma bias

This time we'll focus on the capacitors and double check
the 8164 PT to make sure it's not running too hot.
Maybe someday change it to a Triad 7993 PT.
Toppscore.

[selloutrr]

When those measurements were taken what was your city AC power voltage?

[Toppscore]

When those measurements were taken what was your city AC power voltage?

It was off the commercial shop power.
I can only assume it was 120v-125v.
Not sure if it was possibly regulated to 115v.

What do you think and share your concern.
Thanks.

[Firestorm]

Trying to verify the Chicago Standard Transformer 8164,
it's production years, it's performance specs,
if it is supposed to be in a vintage Fender amp, etc.
Decided to give the amp a Sprague Atom filter capacitor job.
I'll get the wattage specs and compare,
but four months ago I had the specs checked as the following:
Secondary: 640 VAC
Rectifier heater: 6.7VAC
Heaters: 5.1VAC
B+: VA 395vdc, VS 394vdc
Output power: ~40W
Miscellaneous: 20ma bias.
Toppscore.

Are you sure you don't have the measurements for the rectifier filaments and the rest of the heaters swapped?

Is that the 5D6 DK #0769? I really doubt that it would have come from the factory with a Stancor/CST power tranny. Those early ones seem to have used on-hand transformer inventory (Leo wasted nothing): the OTs seem to have been 4-ohm secondary models, like the 2485 found on early Twins (Fender did the same thing with the 3x10 Bandmasters); the PTs didn't have bias taps so they dropped one off the HT winding, so I would expect it to be a Triad from 5B6 or 5C6 (if such a thing ever existed) models, or from a Twin, Pro or Super. All of those were wound for a 5U4 so could more or less handle the dual 5Y3s. If I had to guess, I'd suspect that someone along the line wanted to make it more like the 5E6 and installed two 5U4s, burning out the winding on the original PT. If it came back to Fullerton for service, it would have gotten a Triad or a Schumacher (depending on when it happened) but a lot of these got serviced in the field, so anything might have been put in. The Stancor was a perfectly good choice.

[Toppscore]

Contacted Patrick at MM regarding mid-1950s 4x10 Bassmans
and their power transformers:
"Toppscore: Thank you for choosing Mercury! Great amp! You are a lucky man!
You would want the Mercury Magnetics FPB-50 which is a single 120 volt.
The MM FPB-50/U is a Universal Primary for 120v or 240v.
Regarding the Stancor/Chicago 8164. To be honest, we only
clone the best sounding transformers out of a particular amp,
and have yet to see a Stancor worth cloning. Let us know if you
would like to order and any questions any time. Thanks! Patrick"

Ouch (I'am assuming the FPB-50 is a Triad 7993 clone).

Well, that tells the story of the Chicago 8164 PT in the Bassman.
Will be considering pulling the Chicago 8164 and installing a MM-FB-50.
Just a consideration, as my voltage/amp man states each of the active
two installed rectifiers are getting 3-amps each.

Maybe the Chicago is a replacement and is the perfect replacement.
Maybe not. Still, who knows when/where it was installed.

At least Mercury Magnetics claimed to have a Triad 7993 replacement.
I sent Patrick of MM some more questions regarding their FBP-50 tranny.

I'll be seeking Triad 7993 power transformer clones at:
Heyboer at Mojo Tone
Mercury Magnetics
Hammond

Does anyone recommend other suppliers of vintage transformers?
Or has old inventory stock?
Thanks. Toppscore

[Toppscore]

Are you sure you don't have the measurements for the rectifier filaments and the rest of the heaters swapped?

Is that the 5D6 DK #0769? I really doubt that it would have come from the factory with a Stancor/CST power tranny. Those early ones seem to have used on-hand transformer inventory (Leo wasted nothing): the OTs seem to have been 4-ohm secondary models, like the 2485 found on early Twins (Fender did the same thing with the 3x10 Bandmasters); the PTs didn't have bias taps so they dropped one off the HT winding, so I would expect it to be a Triad from 5B6 or 5C6 (if such a thing ever existed) models, or from a Twin, Pro or Super. All of those were wound for a 5U4 so could more or less handle the dual 5Y3s. If I had to guess, I'd suspect that someone along the line wanted to make it more like the 5E6 and installed two 5U4s, burning out the winding on the original PT. If it came back to Fullerton for service, it would have gotten a Triad or a Schumacher (depending on when it happened) but a lot of these got serviced in the field, so anything might have been put in. The Stancor was a perfectly good choice.

Firestorm. I can agree with your ideas. I can better understand there was
a time during 1961 when this amp had a Jensen P10Q installed with new 1961 wiring.
There were 1960s experiments on Bassmans, Twins & Bandmasters
to change components for the Holy Grail Tone

My Bassman also had dual 5AR4 rectifier tubes before I invested into
two correct 1954 GE-5Y3GT rectifiers. Maybe in 1961 the 5AR4 rectifiers
and the Chicago Transformer 8164 were mated by intentional design???

The Chicago 8164 has been in the 5D6 Bassman for over 50 years.
Hoping it was factory installed, and it could be from suppliers offering
demo test products seeking a Fender supply contract.
Since the Bassman is in the shop this week, I've done more research;
I'll live as the 8164 is a replacement PT ~ probably been in denial haha

General Internet researched comments indicates the Chicago Standard 8164
is a good solid tranny and a great replacement for that time.
Currently double checking the PT specs as I want to know bottom-line
8164's output numbers ~ as I'm investing in a variac to manage this particular
1954 Bassman at 110v-115v.
Want to make sure the dual rectifiers are getting 3/amps each.
Was told they were today. Will get a full report on Friday.
The Bassman is having six Sprague Atom filter capacitors installed, today.

Honestly, I was trying to sell it in this cash-dead market.
Yet, with all the work, effort, 1955 speaker, filter cap components,
1954 dual rectifiers replaced, etc. invested into my 5D6,
I'm going to keep it, play it and hook-up my 1962 Reverb tank for effects.

Firestorm, thanks again for the comments. Toppscore

[Firestorm]

Want to make sure the dual rectifiers are getting 3/amps each.
Was told they were today. Will get a full report on Friday.

The 5Y3s draw only 2 amps each. It's part of what makes this amp (and the 5D8 Twin) so unusual -- the use of two 5Y3 rectifiers instead of the dual 5U4s that came later in the 5D6-A and the 5E8 (unless there was a 5D8-A).

It poses a dilemma for you, though. MM's 7993 clone will support dual 5U4s and will have a bias tap. Neither of those things would have been true of your amp originally. The 7993 goes in the 5D6-A. The earlier 5D6 would have had something else.

[Toppscore]

Want to make sure the dual rectifiers are getting 3/amps each. Was told they were today. Will get a full report on Friday.

The 5Y3s draw only 2 amps each. It's part of what makes this amp (and the 5D8 Twin) so unusual -- the use of two 5Y3 rectifiers instead of the dual 5U4s that came later in the 5D6-A and the 5E8 (unless there was a 5D8-A).
It poses a dilemma for you, though MM's 7993 clone will support dual 5U4s and will have a bias tap. Neither of those things would have been true of your amp originally. The 7993 goes in the 5D6-A. The earlier 5D6 would have had something else.

============


You're right about the Bias Tap. I do not know anything about
positives or negatives towards the PT having a bias tap or not.
Plus the mounting bracket for the amp to the top panel connection
will need to be traded.

The original 5D6 Bassman's 5Y3 rectifiers and current NOS 1954 5Y3's
take 2-amps each or 4-amps total. The MM FPB-50 replacement gives
the two dual 5Y3 rectifiers 5v/4a. This should be perferct, don't you think?
I am open for discussion, as there are other 7993 clone amps on the market.
As mentioned below, someone recommends Heyboer has an exact 7993 duplicate.

But, gathering from what you stated, if I'm correct, you do not believe
the Triad 7993 was installed in the 1954 5D6 Bassmans, but were installed
in the 1955 5D6A Bassmans? Please keep me accurate on this.

The first 5D6 "replacement" rectifiers were 5AR4s Groove Tubes (I still have them)
which commanded 3-amps each. Therefore, the 8164 Chicago/Stancor PT
might have been "pushing it" hard and hot for 50 years

Firestorm. What do you believe Fender shipped for power transformers
during that first production run in November 1954.

If it was not the Chicago Standard 8164 nor the Triad 7993, what do you think or can deduct?

What positives and/or negatives would be generated if a Triad 7993 or the
Mercury Magnets FBP-50 was installed in my November 5D6 Bassman?

Thanks for sharing. Toppscore


Following are three comments I researched of the Internet.
===============
Check out this Internet posted comment complaint:
I just got the MM parts in today. When I talked to them, they assured me that the taps running to the rectifier tubes were 5V@6A. They're not. They're 5V@3A just like the transformer I have installed. The reason that it should be 5V@6A is because each of the 5U4 rectifier tubes draws 3A. The current replacement PT being used is rated at 5V@3A to the rectifier tubes. This is great for a single 5U4 rectifier tube. The problem presents itself when you have two 5U4 rectifier tubes that each draw 3Amps. The current 5v@3a PT isn't built to handle the needed required load.

==============
More comments from the above person:
I also discovered that Mojo supplies a Fender Bassman power transformer with this amp. This transformer does not run enough current to the rectifier tubes. I have now installed a new custom Heyboer transformer that is identical to the Triad 7993 transformer that was put in the LPTT in 1957.

==============
Amp review towards = Victoria Model 50212-T 45 watt Bassman Clone:
One deviation from original design was the elimination of the dual 5U4 power supply. When this amp was designed, the 5AR4 was not a tube that was widely available. The 5U4 was only game in town for high current application. Trouble is, they pull a lot of heater current and that necessitates a big-ass power transformer. I feel that the stock power tranny, the Triad 7993, was the absolute minimum that could have been used to handle them. By using the GZ-34, we get the same attack dynamic as the dual 5U4, keeps the tranny much cooler & happier.

[Firestorm]

The first 5D6 "replacement" rectifiers were 5AR4s Groove Tubes (I still have them)
which commanded 3-amps each. Therefore, the 8164 Chicago/Stancor PT
might have been "pushing it" hard and hot for 50 years

Firestorm. What do you believe Fender shipped for power transformers
during that first production run in November 1954.

If it was not the Chicago Standard 8164 nor the Triad 7993, what do you think or can deduct?

What positives and/or negatives would be generated if a Triad 7993 or the
Mercury Magnets FBP-50 was installed in my November 5D6 Bassman?

Thanks for sharing. Toppscore

5AR4s are also 2 amp filament tubes (1.9 amps actually), so if your GT 5AR4s pulled 3A, they weren't actually 5AR4s.

Double check with Mercury as to the rating of the 5V filament winding. I can't believe they would sell a replacement for mid-50s Bassman amps that wouldn't support 6A for two 5U4s.

Nothing wrong with your using the 7993. That transformer remained in the Fender arsenal for several years. You don't have to connect the bias tap if you want to keep your amp "original."

I just assume that if yours originally had the bias tap (7993) Fender would have used it. This model was Fender's first foray into fixed bias so it seems reasonable that before they specced PTs with the bias tap, they would experiment with generating bias the other way.

I have no clue what PT Fender might have used in the earliest 5D6s: the thing that throws me is the Z-mount PT. The tranny from the same era Twin (5C8/5D8) would have worked fine, but it's X-mount. Some of the 5D Bassman examples share the same OT as the Twin, though.

[Toppscore]

5AR4s are also 2 amp filament tubes (1.9 amps actually), so if your GT 5AR4s pulled 3A, they weren't actually 5AR4s.

They were Groove Tube 5AR4s, just mis-assumed the 3a.



Double check with Mercury as to the rating of the 5V filament winding. I can't believe they would sell a replacement for mid-50s Bassman amps that wouldn't support 6A for two 5U4s.

Mercury responded towards that other person's critical comments ~
MM stated that their FBP-50 will handle 5U4s.



Nothing wrong with your using the 7993. That transformer remained in the Fender arsenal for several years. You don't have to connect the bias tap if you want to keep your amp "original."

Really not too concerned about "original" with most my amps.
My thinking is that amps are like cars and need to replace some things.
Don't cha think? I held on to the original filter caps till this week.
If I can procure a Triad 7926 tranny clone or a Triad 7993 tranny clone,
will they be better than the currently installed Chicago 8164?
Maybe, maybe not. Maybe a different tone. That's what I'm investigating.

Speaker recones are like tires and mufflers changed. What can a vintage
amp owner do to maintain original tone and yet not ruin vintage cones
or capacitors, etc.? My 1960 6G4 plays and sounds incredible,
but the cones are very thin/worn. Therefore if the Chicago 8164 PT
is not original, it's not the worst thing in the world.
With this amp, some caps/resistors/tubes, speaker cones, PT and a
NOS leather handle not being original is not too bad. What do you think?
Personally, I'll take no rust and no corrosion with 95% original parts,
than a corroded rusted-out 100% original amp.
Question: Are there REALLY any truly all original 1940s/1950s amps?
Wear tear weather heat moisture rips dings 125volts stretched-handles.

But, on the other hand, as you say, trying to get NOS or
period correct replacement parts is the best way to go.
Firestorm. You know your early 1950s amps



I just assume that if yours originally had the bias tap (7993) Fender would have used it. This model was Fender's first foray into fixed bias so it seems reasonable that before they specced PTs with the bias tap, they would experiment with generating bias the other way.

This thing about 3/amps versus 2/amps for powering the rectifier tubes,
and the 7993 "bias tap" got me wondering . . . . I did some research
and dug up my notes:
"During 1954, Fender installed the Triad 7926 power transformer;
Triad 2770 output transformer and the Triad 14560 choke into
the 5D6 Bassmans. Fender changed to the Triad 7993 installed
within the 5D6-A Bassmans in January 1955. At that time, Fender
changed from the 5Y3 rectifier tubes to the 5U4 rectifiers".

So, I have been barking up the wrong tree. For whatever reason,
I had Triad's 7993 PT on my mind, when it should be Triad 7926 PT
for the November 1954 5D6 Bassman.
Firestorm, does the Triad 7926 PT change the game?
Was it not you earlier that mentioned Fender probably cleaned-up
inventory when producing the three prototype production 5D6 and 5D6A
Bassmans runs before introducing the 1955 5E6 4x10 Bassman?
What do you think about the Triad 7926 power transformer?




I have no clue what PT Fender might have used in the earliest 5D6s: the thing that throws me is the Z-mount PT. The tranny from the same era Twin (5C8/5D8) would have worked fine, but it's X-mount. Some of the 5D Bassman examples share the same OT as the Twin, though.

I'm learning, so not sure about mounting or the Twin comparisons.
Mercury told me that their FBP-50 (7993) would fit just fine (I sent pictures
of the installed trannys and chassis), but stated I'd need to trade/swap
the PT "L" shaped mounting bracket.

Now, it's better to understand the Triad "7926" PT, if they exist,
do not have a bias tap, andif someone has produced a clone
Anybody know the Triad 7926 PT features and specs?


So, Firestorm, do you own a 1954 5D6? Or, what do you have
and how do you know what you know? Ever worked on one?

Thanks for your help. Toppscore