New (to me) amp - Speaker connection question

[txtune]

I lucked into this amp yesterday. I am curious about the speaker connections. There are four terminals at each speaker connection. It appears there are two white wires, one black, and one green connected from the OPT to each terminal. The black wire is grounded to the chassis, the green wire is connected to the 9 pin socket in the middle-front of the amp, and the two white wires are landed without any other connections.

Is this setup for connecting different types of speakers? How would 8ohm speakers connect, with only two wires, to these terminals?

Thanks!

[shooter]

I would ohm from black to each white on both OT's.  my guess is common (black) xohms on one white, 2xohms on the other white.
they will probably be low ohms, so zero out your leads.

[txtune]

I would ohm from black to each white on both OT's.  my guess is common (black) xohms on one white, 2xohms on the other white.
they will probably be low ohms, so zero out your leads.

Should this be done with no power supplied? Or with a low amount, 10-20vac?

[mresistor]

Are there any brand markings or part # markings on the OT's?

[txtune]

Are there any brand markings or part # markings on the OT's?

There are these numbers on top of the covers.

[shooter]

with no power supplied?

you need a meter that can ohm < 1 ohm


otherwise do the vac and calculate ( you can pull the PA tubes to get to the primary sides without un-soldering, i believe)

[PRR]

> There are these numbers on top of the covers.

Transformers are from an EICO HF50 or similar.

https://www.ampslab.com/SCHEMATICS/LowRes/EicoHF5060.jpg

[sluckey]

High resolution schematic...

     https://www.thetubestore.com/lib/thetubestore/schematics/Eico/Eico-HF-50-HF-60-Schematic.pdf

[txtune]

Transformers are from an EICO HF50 or similar.

https://www.ampslab.com/SCHEMATICS/LowRes/EicoHF5060.jpg

How were you able to tell? Now that I am looking at other EICO amps I see more similarities. I connected some Heresy 1 speakers to the 8 ohm terminals and it sounded really, really, really good.

If you were guessing, do you think someone took parts from a couple EICO mono amps and made a stereo amp? 

[shooter]

maybe 
I let the "2 white wires" from earlier post slide, till now, are you color blind 


glad it sounds good, clean it up play it loud!

[sluckey]

Here's some more info. Parts List, page 4 shows your OT.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjAreuaj9PuAhWqrVkKHfd9BLAQFjARegQIFhAC&url=https%3A%2F%2Fwww.vintageshifi.com%2Frepertoire-pdf%2Fpdf%2Ftelecharge.php%3Fpdf%3DEico-HF-52-Service-Manual.pdf&usg=AOvVaw2D6MTwYoXLAy5GhZfoW0kR

[sluckey]

If you were guessing, do you think someone took parts from a couple EICO mono amps and made a stereo amp?

That's a good guess. Would explain no writing on the chassis.

[txtune]

That's a good guess. Would explain no writing on the chassis.

It sounds great, some of the soldering and wiring looks rough. I am thinking about putting it in a new enclosure, cleaning up the wires a bit, adding a PEM, and some binding posts for speakers connections.

[sluckey]

What are the numbers on the power transformer? I'm asking because it looks a bit small to be powering two 50 watt power amps.

[txtune]

What are the numbers on the power transformer? I'm asking because it looks a bit small to be powering two 50 watt power amps.

Let me go look. What is the most efficient way to drain every cap? Or do I need to drain each of the large ones individually?

[sluckey]

Use two gator clip test leads and a 100K resistor. Connect one end of the resistor to chassis ground and connect the other end of the resistor to pin 8 of the rectifier tube socket.

Or, if you want to have a permanent drain, solder a 220K 3W resistor between pin 8 of the rectifier socket and chassis ground.

[txtune]

Or, if you want to have a permanent drain, solder a 220K 3W resistor between pin 8 of the rectifier socket and chassis ground.

Really? This is not some cruel joke where the amp blows up after I do this right? "That new kid fell for the old permanent drain trick hahaha..."

[sluckey]

Look at this schematic in the area of rectifier pin 8...

     http://sluckeyamps.com/phoenix/phoenix.pdf

[txtune]

Look at this schematic in the area of rectifier pin 8...

     http://sluckeyamps.com/phoenix/phoenix.pdf

Got it. They should have just built them all like that.

Let me get the PT numbers.

[shooter]

not some cruel joke where the amp blows up after I do this right?

Naw Steve's nice, I woulda had you use 1 gator, no R, that way you get a good SNAP, and arc 

[sluckey]

That's my way too. The louder the firecracker, the stronger the cap! 

[txtune]

That's my way too. The louder the firecracker, the stronger the cap! 

Alright, alright.

Here is a photo of the rectifier socket, there is an cap and a 1k resistor on pin 8. Did someone already set this one up to drain? I am not sure what the 1k resistor is connected to though... something metal that is attached to the chassis.

[txtune]

Also, the socket next to the rectifier has no wires attached to the pins. It came with a relay plugged into it, see photo. A relay plugged into a socket connected to nothing, expect the case, is not serving any functional purpose... right??

[sluckey]

WHAT ARE THE NUMBERS ON THE PT???

[txtune]

WHAT ARE THE NUMBERS ON THE PT???

I AM GETTING THERE!!! GOING TO HAVE TO UNBOLT IT!!!

[sluckey]

You're not likely to find any numbers on the bottom of that PT.

[txtune]

You're not likely to find any numbers on the bottom of that PT.

There certainly are not any numbers on the outside.

Is the 1k resistor a permanent drain?

[PRR]

> power transformer? I'm asking because it looks a bit small to be powering two 50 watt power amps.

Also that is not enough rectifier for heavy use. I do agree it may be 3/4 of two mono amps. So not likely to blow the lid off the cow-palace. *May* be a fine livingroom amp. If it does not burn-up just idling.

The Delay Relay is VERY precious today.

A working pair of the EICO OTs may be worth more to a hi-fi-natic than to you.

[txtune]

Also that is not enough rectifier for heavy use. I do agree it may be 3/4 of two mono amps. So not likely to blow the lid off the cow-palace. *May* be a fine livingroom amp. If it does not burn-up just idling.

The Delay Relay is VERY precious today.

The relay was plugged into a socket with no wires connected. Is that likely something the original builder did not get around to?

[sluckey]

Is the 1k resistor a permanent drain?

No. And the metal thing it's connected to is another power resistor. That style was common in the '50s and '60s.

[shooter]

when this tool is as common as a #2 Philips, you know you're workin on scary sheeeet


quick look appears the relay switches ground to the pre   

[txtune]

No. And the metal thing it's connected to is another power resistor. That style was common in the '50s and '60s.
[/quote]

Ok, if I connect a 3W 220K onto the same pin (#8) and take it to chassis ground it will become a permanent drain, correct?

[txtune]

quick look appears the relay switches ground to the pre 

How does that relay switch anything? The pins on the socket are not connected to anything.

[sluckey]

Ok, if I connect a 3W 220K onto the same pin (#8) and take it to chassis ground it will become a permanent drain, correct?

déjà vu?

How does that relay switch anything? The pins on the socket are not connected to anything.

I know you know the answer to this. 

[txtune]

Ok, if I connect a 3W 220K onto the same pin (#8) and take it to chassis ground it will become a permanent drain, correct?

déjà vu

Fair enough

How does that relay switch anything? The pins on the socket are not connected to anything.

I know you know the answer to this. 

I took a stab at it several posts back, was my guess correct or not?

[DummyLoad]

Also that is not enough rectifier for heavy use. I do agree it may be 3/4 of two mono amps. So not likely to blow the lid off the cow-palace. *May* be a fine livingroom amp. If it does not burn-up just idling.

The Delay Relay is VERY precious today.

The relay was plugged into a socket with no wires connected. Is that likely something the original builder did not get around to?

no wires, no workey. obviously.   

--pete

[DummyLoad]

someone's piss-poor implementation/hack of a pair of HF-50 type monoblock amps into a single chassis.


power supply is waaaay underrated - you need transformer much larger than that to push both channels to full power dependably. the single GZ34/5AR4 is also very much underrated for a 100W platform. 50W yes, 70W is stretching it.

the construction quality is subpar. sell the output transformers to a collector, or start over if you want something that's not going to crater prematurely and possibly destroy those highly regarded output transformers.


respectfully,


--pete

[shooter]

The pins on the socket are not connected to anything.

my comment was meant to have you look at schematic, figure out which parts, if any, are no longer needed since no wires.


i like cats, not one, so curiosity hasn't killed me yet, close, but.............. 

[txtune]

someone's piss-poor implementation/hack of a pair of HF-50 type monoblock amps into a single chassis.

power supply is waaaay underrated - you need transformer much larger than that to push both channels to full power dependably. the single GZ34/5AR4 is also very much underrated for a 100W platform. 50W yes, 70W is stretching it.

the construction quality is subpar. sell the output transformers to a collector, or start over if you want something that's not going to crater prematurely and possibly destroy those highly regarded output transformers.

Thanks Pete. I have no idea what they are worth, I will have to do some digging around online.

Is there a stereo amplifier design you would suggest as a good way to use these OTs?

[txtune]

my comment was meant to have you look at schematic, figure out which parts, if any, are no longer needed since no wires.


i like cats, not one, so curiosity hasn't killed me yet, close, but.............. 

[sluckey]

The Delay Relay is VERY precious today.

I'm rich!   

[shooter]

Is there a stereo amplifier design

the design is good, the power supply is weak
if it's mine and I want to keep it;
I'd find a 400mA PT, (doublecheck) convert to diode rectifier and big caps, in a new box

[txtune]

https://youtu.be/98958txVSrE9819]
The Delay Relay is VERY precious today.

I'm rich!   

[DummyLoad]

someone's piss-poor implementation/hack of a pair of HF-50 type monoblock amps into a single chassis.

power supply is waaaay underrated - you need transformer much larger than that to push both channels to full power dependably. the single GZ34/5AR4 is also very much underrated for a 100W platform. 50W yes, 70W is stretching it.

the construction quality is subpar. sell the output transformers to a collector, or start over if you want something that's not going to crater prematurely and possibly destroy those highly regarded output transformers.

Thanks Pete. I have no idea what they are worth, I will have to do some digging around online.

Is there a stereo amplifier design you would suggest as a good way to use these OTs?

duplicate the HF-50/HF-60 amp. if you use a common power transformer, then procure a part that can adequately power a 100W class amp, the hammond 300 series lineup has some excellent choices that will provide the 500V B+ specified.

better low freq. performance and a quieter amp with a solid state rectified power supply. recommend a pi filter arrangement with larger filters, since this is a ultra-linear amp for hi-fi. consider a dual monoblock plan with the only commonality being the chassis.

good luck and happy rosin smokin'

--pete

[DummyLoad]

The Delay Relay is VERY precious today.

I'm rich!   

40 bux each - flip em' for beer & bait $$.


--pete

[txtune]

duplicate the HF-50/HF-60 amp. if you use a common power transformer, then procure a part that can adequately power a 100W class amp, the hammond 300 series lineup has some excellent choices that will provide the 500V B+ specified.

better low freq. performance and a quieter amp with a solid state rectified power supply. recommend a pi filter arrangement with larger filters, since this is a ultra-linear amp for hi-fi. consider a dual monoblock plan with the only commonality being the chassis.

I like the idea of dual monoblock sharing a chassis. If the only commonality is the chassis, I would need two power transformers, correct? 

[DummyLoad]

duplicate the HF-50/HF-60 amp. if you use a common power transformer, then procure a part that can adequately power a 100W class amp, the hammond 300 series lineup has some excellent choices that will provide the 500V B+ specified.

better low freq. performance and a quieter amp with a solid state rectified power supply. recommend a pi filter arrangement with larger filters, since this is a ultra-linear amp for hi-fi. consider a dual monoblock plan with the only commonality being the chassis.

I like the idea of dual monoblock sharing a chassis. If the only commonality is the chassis, I would need two power transformers, correct?

yes. two power transformers, two chokes, etc..

--pete

[shooter]

the pics look like you have 2 chokes already?

[txtune]

the pics look like you have 2 chokes already?

Yes, there are two chokes.

[shooter]

I'd bust out the meter, measure the VDC against what's on the schematics posted earlier.  start at the cathodes of the PA (.5vdc), bias vdc (-35).  and the 500vdc on the power rail, if their close, do the preamp plate voltage.


if they fall in line;
i'd monitor the PA cathodes, 2 meters, one one each pair and run the amp with music at 50% for maybe 15-30minutes (what I call the smoke test:)
If you have a temp monitor, measure the PT temp at start, then every 5 minutes of play