Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Nov Mon 18, 2019 12:21 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 15 posts ] 
Author Message
 Post subject: Identifying connector and part on vintage twin EL84 amp
PostPosted: Mar Mon 25, 2019 1:00 pm 
Member
User avatar

Joined: Oct Fri 12, 2018 11:07 am
Posts: 169
Location: FL
Hi,

I have a vintage tube amp with me for a while. From the looks, it seems to be a homemade or designed by someone for the personal use I guess. Since, I already see that the power supply filter cap lead wasn't soldered and just twisted. I've attached the lo-res pics of the amplifier below. (I've also attached a google drive link for the pictures of the same at higher resolution).

https://drive.google.com/drive/folders/ ... sp=sharing

I've circled the parts on the amp. One is a weird rectangular connector. The other one is a some kind of component under the chassis. Seems like those old semiconductor rectifiers. But since this already had a 5U4GB rectifier it doesn't make sense for them to include another rectifier. Also the other tubes are EL84(x2), one 6AU6 and 0A2 (x2. It has a chunky choke and a monstrous power transformer. Heck yeah, its almost the size of my hand and weighs at least 2/3rd of the 18 lbs of the amp :mrgreen: !! I'm currently planing to restore it after revere engineering to get the schematics.

Also have to figure out if it needs, where the audio transformer goes and if so what type is needed. There is plenty of space to put one too!

Thanks,
Raul

UPDATE: Please check the link to the schematic I was able to draw from the wiring. Sorry for the clumsy drawing! :)

https://drive.google.com/file/d/1dTZLnV ... sp=sharing

Attachment:
rsz_schematics.jpg
rsz_schematics.jpg [ 75.26 KiB | Viewed 744 times ]


Attachments:
Bottom Pic 1.jpg
Bottom Pic 1.jpg [ 345.47 KiB | Viewed 839 times ]
Connector.jpg
Connector.jpg [ 263.04 KiB | Viewed 839 times ]
PHOTO-2019-03-24-21-34-49_2.jpg
PHOTO-2019-03-24-21-34-49_2.jpg [ 32.29 KiB | Viewed 839 times ]
PHOTO-2019-03-24-21-34-49.jpg
PHOTO-2019-03-24-21-34-49.jpg [ 56.75 KiB | Viewed 839 times ]
PHOTO-2019-03-24-21-34-50.jpg
PHOTO-2019-03-24-21-34-50.jpg [ 42.82 KiB | Viewed 839 times ]
rsz_1s-l1600.jpg
rsz_1s-l1600.jpg [ 54.09 KiB | Viewed 836 times ]

_________________
If we did all the things we are capable of, we would literally astound ourselves -Thomas Edison


Last edited by Vintage Collector on Mar Tue 26, 2019 10:44 pm, edited 5 times in total.
Top
 Profile  
 
 Post subject: Re: Help with connector and part on vintage twin EL84 amp
PostPosted: Mar Mon 25, 2019 2:14 pm 
Member

Joined: Feb Thu 28, 2019 7:48 pm
Posts: 392
Location: Lawrenceville, Illinois 62439
FWIW, that connector looks like a Cinch Jones receptacle which used to be used on an 8 wire antenna rotor chrome wall plate. (Amongst other uses, I'm sure)


Top
 Profile  
 
 Post subject: Re: Help with connector and part on vintage twin EL84 amp
PostPosted: Mar Mon 25, 2019 2:21 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5360
Location: Rochester NY USA
The circled parts are a pair of selenium rectifiers and an 8-pin "Jones" connector. The rectifiers may be for a fixed bias supply, not commonly used with 6BQ5s. The VR tubes are likely for screen voltage supply, in series for 300V. The circuit could be parallel single-ended, since there's only one amplifier tube, nothing for phase inverter. In that case, output transformer would be 4-5K that's rated for 100 mA or more. If the 6AU6 is a phase inverter for push-pull, the amp will require about 30V peak-peak drive. Output transformer for push-pull would be about 8-10K center-tapped.

One other possibility - this is a regulated DC power supply, not an audio amp.

_________________
My web page: https://bit.ly/2rxq4qx


Top
 Profile  
 
 Post subject: Re: Help with connector and part on vintage twin EL84 amp
PostPosted: Mar Mon 25, 2019 5:06 pm 
Member

Joined: Sep Tue 30, 2014 6:08 am
Posts: 4779
Location: Norfolk, VA
If you need the plug for that connector, Jameco, offers this:

https://www.jameco.com/z/P-308-CCT-Cinch-Connectors-8-Position-Plug-Connector-Cable-Clamp-with-Hood_2286823.html

_________________
Brian
"Capacitor Cosmetologist since 1979"
USN Retired 1984-2006 (Avionics/Cal)


Top
 Profile  
 
 Post subject: Re: Help with connector and part on vintage twin EL84 amp
PostPosted: Mar Mon 25, 2019 8:25 pm 
Member
User avatar

Joined: Oct Fri 12, 2018 11:07 am
Posts: 169
Location: FL
@Brian and @Yarehobbiesso$ Thank you very much for the info! :)

_________________
If we did all the things we are capable of, we would literally astound ourselves -Thomas Edison


Top
 Profile  
 
 Post subject: Re: Help with connector and part on vintage twin EL84 amp
PostPosted: Mar Mon 25, 2019 8:28 pm 
Member
User avatar

Joined: Oct Fri 12, 2018 11:07 am
Posts: 169
Location: FL
Tom Bavis wrote:
The circled parts are a pair of selenium rectifiers and an 8-pin "Jones" connector. The rectifiers may be for a fixed bias supply, not commonly used with 6BQ5s. The VR tubes are likely for screen voltage supply, in series for 300V. The circuit could be parallel single-ended, since there's only one amplifier tube, nothing for phase inverter. In that case, output transformer would be 4-5K that's rated for 100 mA or more. If the 6AU6 is a phase inverter for push-pull, the amp will require about 30V peak-peak drive. Output transformer for push-pull would be about 8-10K center-tapped.

One other possibility - this is a regulated DC power supply, not an audio amp.


Hi Tom,

I've drawn the schematic from the wiring that was already present in the device. Please take a look at the link in the original post under "update".

Ohh no! I hope that this isn't a power supply! That never crossed my mind.

Sorry for posting link from another website, but I found a similar one like mine.
https://www.diyaudio.com/forums/tubes-v ... lator.html

_________________
If we did all the things we are capable of, we would literally astound ourselves -Thomas Edison


Last edited by Vintage Collector on Mar Mon 25, 2019 8:31 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Help with connector and part on vintage twin EL84 amp
PostPosted: Mar Mon 25, 2019 8:30 pm 
Member
User avatar

Joined: Oct Fri 12, 2018 11:07 am
Posts: 169
Location: FL
Guys, I've added an UPDATE with a link to the schematics.

_________________
If we did all the things we are capable of, we would literally astound ourselves -Thomas Edison


Top
 Profile  
 
 Post subject: Re: Help with connector and part on vintage twin EL84 amp
PostPosted: Mar Mon 25, 2019 10:55 pm 
Member
User avatar

Joined: Aug Fri 09, 2013 1:01 am
Posts: 521
Location: Mount Arlington, NJ 07856
Google certainly makes it tough to read the schematic. No option to rotate it or download?

In the pictures I see two transformers. The smaller one looks like it could be a choke. Is that L in your schematic? And I'm assuming the larger one is the power transformer. I don't see an audio output transformer to drive the speaker. Point A looks like either the speaker output or a connection for plate voltage. I'm not sure if you can drive a speaker directly from a tube without a transformer. I fail to see where the tube plates get their voltage from. And what are the dotted line connections? Why are they dotted? This is puzzling indeed.


Top
 Profile  
 
 Post subject: Re: Help with connector and part on vintage twin EL84 amp
PostPosted: Mar Tue 26, 2019 12:14 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5360
Location: Rochester NY USA
Looks like a regulated power supply to me. Two pots adjust output voltage and a negative bias supply (selenium rectifiers for the minus supply)

_________________
My web page: https://bit.ly/2rxq4qx


Top
 Profile  
 
 Post subject: Re: Help with connector and part on vintage twin EL84 amp
PostPosted: Mar Tue 26, 2019 5:37 am 
Member
User avatar

Joined: Oct Fri 12, 2018 11:07 am
Posts: 169
Location: FL
tunerman wrote:
Google certainly makes it tough to read the schematic. No option to rotate it or download?

In the pictures I see two transformers. The smaller one looks like it could be a choke. Is that L in your schematic? And I'm assuming the larger one is the power transformer. I don't see an audio output transformer to drive the speaker. Point A looks like either the speaker output or a connection for plate voltage. I'm not sure if you can drive a speaker directly from a tube without a transformer. I fail to see where the tube plates get their voltage from. And what are the dotted line connections? Why are they dotted? This is puzzling indeed.


There is a download button next to the print button at the top right corner.

The smaller ones is a large choke. There its only one giant power transformer (450-0-450VAC). Yes, there is no audio output transformer. Since it goes from the filter cap to the Pin 7 of 6BQ5 its plate voltage. The two dotted connections are from the pin 5 & 6 of the 6AU6 pentode.

BTW I never designed this. I just drew the schematics that was already present. I see that at three placed the wires where just twisted and aren't soldered. Looks incomplete to me. But at the 8 pin connector at Pin 7&5 I get 300+VDC. As others have mentioned I'm starting to feel this could be a power supply just like the Heathkit IP-17 I've. It too have those big 6L6GC tubes. Maybe the 6BQ5 does something like that. The 0A2 is what makes me think its a PSU.

_________________
If we did all the things we are capable of, we would literally astound ourselves -Thomas Edison


Top
 Profile  
 
 Post subject: Re: Help with connector and part on vintage twin EL84 amp
PostPosted: Mar Tue 26, 2019 5:41 am 
Member
User avatar

Joined: Oct Fri 12, 2018 11:07 am
Posts: 169
Location: FL
Tom Bavis wrote:
Looks like a regulated power supply to me. Two pots adjust output voltage and a negative bias supply (selenium rectifiers for the minus supply)


Now, that I look more deeper at it, it seems to be right with what you say. The previous person also if you see from the pics has labelled near the pots positive adjust and neg adjust with pencil. If I want to convert this to a good amp which circuit design would you recommend with the 6BQ5s. There is lot of space in the chassis and I can add a good audio transformer and mod it to become an amp. The power transformer is also quite powerful I guess.

_________________
If we did all the things we are capable of, we would literally astound ourselves -Thomas Edison


Top
 Profile  
 
 Post subject: Re: Identifying connector and part on vintage twin EL84 amp
PostPosted: Mar Wed 27, 2019 4:16 am 
Member
User avatar

Joined: Oct Fri 12, 2018 11:07 am
Posts: 169
Location: FL
Guys, which is better Single ended or Push-Pull mode? I'm planning to buy an audio output transformer and components to convert this to an amp.

_________________
If we did all the things we are capable of, we would literally astound ourselves -Thomas Edison


Top
 Profile  
 
 Post subject: Re: Identifying connector and part on vintage twin EL84 amp
PostPosted: Mar Wed 27, 2019 7:01 am 
Member

Joined: Aug Wed 24, 2011 4:35 am
Posts: 4575
Location: Sunnyvale CA
Vintage Collector wrote:
Guys, which is better Single ended or Push-Pull mode? I'm planning to buy an audio output transformer and components to convert this to an amp.


Better? For almost all intents and purposes, a properly designed push-pull is superior in most respects. It will certainly provide more power than a single-ended EL84 (15ish watts instead of 4ish watts) and I don't like the idea of parallel single-ended to get make up the power difference, and that is essentially never done. There is a cult that surrounds single-ended amplifiers, mama told to never join a cult.

I would suggest one of the many ultralinear 6v6 or EL84 designs from the mid-late 50s, they were pretty well figured out by then. And put a nice single-ended bandpass filter with a rolloffs around 15-20 Hz and maybe 15 Khz on the input. That will keep the amp out of trouble (from signals that it cannot play) and have no consequential negative side effects for music. All that attempting to beat that will do is cause massive distortion.

Brett


Top
 Profile  
 
 Post subject: Re: Identifying connector and part on vintage twin EL84 amp
PostPosted: Mar Sat 30, 2019 2:51 pm 
Member
User avatar

Joined: Oct Fri 12, 2018 11:07 am
Posts: 169
Location: FL
Brett_Buck wrote:
Vintage Collector wrote:
Guys, which is better Single ended or Push-Pull mode? I'm planning to buy an audio output transformer and components to convert this to an amp.


Better? For almost all intents and purposes, a properly designed push-pull is superior in most respects. It will certainly provide more power than a single-ended EL84 (15ish watts instead of 4ish watts) and I don't like the idea of parallel single-ended to get make up the power difference, and that is essentially never done. There is a cult that surrounds single-ended amplifiers, mama told to never join a cult.

I would suggest one of the many ultralinear 6v6 or EL84 designs from the mid-late 50s, they were pretty well figured out by then. And put a nice single-ended bandpass filter with a rolloffs around 15-20 Hz and maybe 15 Khz on the input. That will keep the amp out of trouble (from signals that it cannot play) and have no consequential negative side effects for music. All that attempting to beat that will do is cause massive distortion.

Brett


Hi Brett,

I think I'll stick with the PP design. I was just going through my vintage stock and found one output transformer with me. It's a NSC-41318-T model 25W transformer. Here is a link to the same type of transformer that I have. Do you think this should be fine or I need to look for the one with 10K itself?
Sorry, I'm not an expert in tubes, just learning through the process and each day.

https://www.worthpoint.com/worthopedia/ ... -149157870

_________________
If we did all the things we are capable of, we would literally astound ourselves -Thomas Edison


Top
 Profile  
 
 Post subject: Re: Identifying connector and part on vintage twin EL84 amp
PostPosted: Mar Sat 30, 2019 2:59 pm 
Member
User avatar

Joined: Oct Fri 12, 2018 11:07 am
Posts: 169
Location: FL
BTW I cleaned up the rust and gave it a small paint job to prevent any further corrosion. Also recapped the supply and fired it up. It does work quite well. Here is a picture of the supply after restoration. Also if anyone had any info on the Power Transformer (Model 128PF-748-1) please let me know.


Attachments:
20190330_135316.jpg
20190330_135316.jpg [ 332.76 KiB | Viewed 596 times ]
20190330_135432.jpg
20190330_135432.jpg [ 215.72 KiB | Viewed 596 times ]
20190330_135438.jpg
20190330_135438.jpg [ 211.36 KiB | Viewed 596 times ]

_________________
If we did all the things we are capable of, we would literally astound ourselves -Thomas Edison
Top
 Profile  
 
Post New Topic Post Reply  [ 15 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 2 guests



Search for:
Jump to:  




























Privacy Policy :: Powered by phpBB