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


It is currently Jul Wed 17, 2019 7:33 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 158 posts ]  Go to page 1, 2, 3, 4, 5 ... 8  Next
Author Message
 Post subject: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 1:46 am 
Member
User avatar

Joined: May Sun 13, 2012 8:12 pm
Posts: 12133
Location: Central PA 16801
hello all,

i need some advice.

I need a replacement output transformer for 6K6 push pull. one leg is out.

my speaker is 4 ohms.

according to the tube manual, P-P 6K6 tubes need a load impedance of 12k ohms.

this universal hammond has many options.

http://www.hammondmfg.com/125.htm

with this universal hammond tranny, i would hook the speaker leads up to pins 2 and 4.

is that close enuf and the way to do it ?

or--cheap way out with parts here in the shop: i have a P-P 6V6 tranny. can i put that in there and use 6V6 tubes in the radio instead of 6K6 ? cathode resistor supplying both tubes is 220 ohms.

this is in a Crosley Eleven, 1117

http://www.nostalgiaair.org/PagesByMode ... 003234.pdf

power tranny is a replacement, not enuf voltage, output tranny is bad...what a deal on this one :cry:

thanks for the help. i have only replaced "like" for "like" when it comes to transformers.

steve

_________________
You have enemies ? Good. That means you've stood up for something, sometime in your life.


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 1:56 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34371
Location: Maryland 20709, USA
dutchrabbit wrote:
my speaker is 4 ohms.
according to the tube manual, P-P 6K6 tubes need a load impedance of 12k ohms.
this universal hammond has many options.
http://www.hammondmfg.com/125.htm
with this universal hammond tranny, i would hook the speaker leads up to pins 2 and 4.
is that close enuf and the way to do it ?
Hi Steve,

That looks fine.

Output from 2 and 4 gives you 11,200 ohm load impedance, close enough to 12K.

Given the ability of p-p 6K6's to produce over 10 watts of audio and draw 72mA Ip, I would use
the type 125D as a minimum, or the 125E to be safe.

Hammond makes nice stuff. I use two of their transformers in one of my products.

- Leigh

On edit: corrected the actual load impedance

_________________
73 de W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Last edited by Leigh on Jul Tue 02, 2013 8:23 am, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 3:56 am 
Member
User avatar

Joined: May Sun 13, 2012 8:12 pm
Posts: 12133
Location: Central PA 16801
hello leigh, good to hear from you.

the 'E' is the more heavy duty one at 80 ma. that should be more than safe, agree ?

so, all i do is hook up the Plate-B+-Plate and then connect the speaker wires to pin 2-4.

i don't have to care what the DC winding resistance is on the new one, right ? (old is 700-0-700 Ohms DC Resistance with meter). i'm asking because from what i know, read, and understand over the years, it is the final match between the tubes and the speaker. reading the DC resistance and comparing DC resistance of the windings of an opt tranny is pretty much useless when chosing a replacement, right ?

for example, if i have a tranny here that is 700-0-700 Ohms, DC resistance with meter and i have another one with the same readings, those numbers are useless to use as "match up and use" for replacement specs, right ? again, talking about DCR not impedence.

DCR is not a way to match up opt trannys, right ?

in well over 300 radios/amps since 1980, i have only replaced one output tranny and two power trannys for a whopping grand total of three. those replacements were all like for like from junk chassis.

power tranny in this crosley, then the output tranny, goodness sake. the economy gods of radio restoration/repair are not with me.

my last two repair/restores (the philco 41-258 and this crosley) have been quite expensive.

thanks in advance for clearing up / confirming my knowledge.

steve

_________________
You have enemies ? Good. That means you've stood up for something, sometime in your life.


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 4:05 am 
Member
User avatar

Joined: Oct Wed 14, 2009 6:36 am
Posts: 5840
Location: New York USA
dutchrabbit wrote:

or--cheap way out with parts here in the shop: i have a P-P 6V6 tranny. can i put that in there and use 6V6 tubes in the radio instead of 6K6 ? cathode resistor supplying both tubes is 220 ohms.

this is in a Crosley Eleven, 1117

http://www.nostalgiaair.org/PagesByMode ... 003234.pdf

power tranny is a replacement, not enuf voltage, output tranny is bad...what a deal on this one :cry:

thanks for the help. i have only replaced "like" for "like" when it comes to transformers.

steve


The 6V6 is a better tube, use your 6V6 output transformer and that big Edcor power transformer I mentioned (in your other post) for enough current. At 285 volts, the 6V6 needs -19 volts bias, so the cathode resistor would be around 275 ohms. The plate to plate load would be 8,000 ohms for 14 watts of audio


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 4:38 am 
Member

Joined: Nov Sat 27, 2010 6:15 pm
Posts: 5449
Truth be known, just about any working order conventional PP output transformer about the same size from your scrounge box will probably work just fine for a normal vintage radio if this is what we are talking about, and I doubt the set would care whether you kept the 6K6's or put in 6V6's, so long as the set is reasonably healthy. That sentence was just too long, I know that. Anyway, so long as there is enough volume, and bias is not twisted unreasonably, it'd take an instrument to tell the difference.

In any case when a section of an output Xformer fails other than just because of a corroded winding to lead connection, which do check for you have nothing to lose, it is usually a shorted capacitor in the plate circuit or an arc/short. Anyway, check and remedy out the cause first.

Best!


Last edited by codefox on Jul Mon 01, 2013 4:58 am, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 4:43 am 
Member

Joined: Sep Thu 23, 2010 6:37 am
Posts: 11408
Location: Powell River BC Canada
The DC resistance is of concern, It sets the DC current in the 125 transformer. It must
not exceed this because it will overheat, while waiting for some program to produce AC watts.
The 125 D is rated at 70 mA DC.

_________________
de
VE7ASO VE7ZSO
Amateur Radio Literacy Club. May we help you read better.
Steve Dow
ve7aso@rac.ca


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 4:53 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34371
Location: Maryland 20709, USA
dutchrabbit wrote:
the 'E' is the more heavy duty one at 80 ma. that should be more than safe, agree ?
so, all i do is hook up the Plate-B+-Plate and then connect the speaker wires to pin 2-4.
Right.

dutchrabbit wrote:
i don't have to care what the DC winding resistance is on the new one, right ?
DCR is not a way to match up opt trannys, right ?
DC resistance is given on schematics for troubleshooting purposes, to aid in identifying open or shorted turns.

DCR provides no useful information as regards matching a transformer to a tube and speaker.

- Leigh

_________________
73 de W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 6:04 am 
Member
User avatar

Joined: Oct Wed 14, 2009 6:36 am
Posts: 5840
Location: New York USA
Deleted, I re-checked the Hammond catalog pages.


Last edited by BikenSwim on Jul Mon 01, 2013 6:05 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 6:05 am 
Member
User avatar

Joined: May Sun 13, 2012 8:12 pm
Posts: 12133
Location: Central PA 16801
thanks for the help guys.

i have no 6v6 pp transformer. i thought i did, but it was single ended.

i will have to go with the 125e. i have nothing else.

the set has been fully restored. it came to me with an insufficient power tranny in it, looks like it was replaced in the late 40's. voltage it too low on hv. the replacement from the 40's is 250-0-250 and i need 325-0-325 as mentioned by another forum member who used one of those and the voltages in the set are near schematic value.

so, i bet when this set had its moment back in the 40's, i would say caps shorted, and killed some transformers, both output and power.

my luck. two of the most expensive parts in this radio...power tranny is the wrong part and the opt is open.

sheesh.

steve

_________________
You have enemies ? Good. That means you've stood up for something, sometime in your life.


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 6:12 am 
Member
User avatar

Joined: May Sun 13, 2012 8:12 pm
Posts: 12133
Location: Central PA 16801
i can't believe what i have been getting myself into.

that philco, now this crosley !

i love it !

steve

_________________
You have enemies ? Good. That means you've stood up for something, sometime in your life.


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 6:23 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34371
Location: Maryland 20709, USA
radiotechnician wrote:
The DC resistance is of concern, It sets the DC current in the 125 transformer. It must
not exceed this because it will overheat, while waiting for some program to produce AC watts.
The 125 D is rated at 70 mA DC.
Huh?
The plate current is set by the element voltages.

The reflected impedance of the speaker through the transformer sets the dynamic load, not the Ib.

Transformer current ratings are maximum permissible, unrelated to tube operation.

- Leigh

_________________
73 de W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 6:30 am 
Member
User avatar

Joined: May Sun 13, 2012 8:12 pm
Posts: 12133
Location: Central PA 16801
i thank you all for the great help.

as i said in my other posting about the power tranny in this set, which really warms up since it is way too small, i know what i need to do.

refinance the car and house and get a power and an opt tranny for this set.

thanks again for the help. i 'll post back when i fork out the dough, (yea. most likely tomorrow) and get this stuff ordered.

steve

_________________
You have enemies ? Good. That means you've stood up for something, sometime in your life.


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 8:40 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34371
Location: Maryland 20709, USA
What about the condos in Miami and Cancun?

Oops... sorry...

- Leigh

_________________
73 de W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 3:43 pm 
Member
User avatar

Joined: May Sun 13, 2012 8:12 pm
Posts: 12133
Location: Central PA 16801
no trips to bermuda this year, for sure.

one more question, the two flexies resistors in this set....i replaced them with half-watt resistors.

should i have replaced them with quarter watts ?

thx.

steve

_________________
You have enemies ? Good. That means you've stood up for something, sometime in your life.


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 5:44 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 20040
Location: Warner Robins, GA
What size speaker does this radio use? Reason I ask is because IIRC the Hammond transformer listed only goes down to 150 Hz. If the speaker is 6" or larger you would want a transformer that has a little better low frequency response. Don't necessarily need response down to 20 Hz, but I'm thinking along the lines of the Edcor transformer series that has a low frequency response down to 70 Hz.

http://www.edcorusa.com/c/65/xppseries

The Hammond 125E is $42.40 at Mouser, whereas the most expensive Edcor transformer in the link I posted is $30.00 and has better low frequency response.

You could then swap to 6V6 tubes and get by with the 10K output transformer.


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 5:50 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34371
Location: Maryland 20709, USA
dutchrabbit wrote:
the two flexies resistors in this set....i replaced them with half-watt resistors.
should i have replaced them with quarter watts ?
No. Half-watt resistors are fine.

The idea of resistors being used as fuses is valid, but it only happens in very limited situations.
You'll only find these in the power supply.

One example that came up in a current thread is an 18-ohm 1/4-watt resistor between the
rectifier cathode and the first filter cap. That's obviously a fuse, in case a filter cap shorts.

I normally use higher-power resistors for all repairs, with 1-watt being the smallest I stock.
Modern 1-watt film resistors are about the size of 1/2-watt carbon comps.

The major reason for the higher power rating is that modern resistors withstand higher temperatures.
Since we don't want the resistors running hot, it's wise to use parts with higher ratings.

- Leigh

_________________
73 de W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 5:53 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34371
Location: Maryland 20709, USA
Tube Radio wrote:
What size speaker does this radio use? Reason I ask is because IIRC the Hammond transformer listed only goes down to 150 Hz. If the speaker is 6" or larger you would want a transformer that has a little better low frequency response. Don't necessarily need response down to 20 Hz, but I'm thinking along the lines of the Edcor transformer series that has a low frequency response down to 70 Hz.
The 150Hz point is only 1dB down.

You don't want response at 120Hz because it will accentuate power supply hum.
The 150Hz rating is totally appropriate for a vintage radio. This ain't hi-fi FM.

- Leigh

_________________
73 de W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 6:09 pm 
Member

Joined: Nov Sat 27, 2010 6:15 pm
Posts: 5449
Agree, most but not all vintage set designs had transformers and speakers that were very inefficient below 150 HZ, and practically deaf abore 5 KHZ. Push pull output does cure multiple sins provided somewhat of a balance exists between the final tubes one way or another. All bets are off if you want to partially repurpose the set to be used for better program quality inputs.


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 6:17 pm 
Member
User avatar

Joined: Oct Wed 14, 2009 6:36 am
Posts: 5840
Location: New York USA
Edcor has an excellent transformer for 8K to 4 ohms, 15 watts and response to 70 Hz, an exact match for your 6V6 tubes for only $20.01 http://www.edcorusa.com/p/357/xpp15-4-8k
The screen connection terminals are for ultra-linear, don't use those for this circuit.


Top
 Profile  
 
 Post subject: Re: Output Transformer Replacement Help / Questions
PostPosted: Jul Mon 01, 2013 6:25 pm 
Member

Joined: Sep Thu 23, 2010 6:37 am
Posts: 11408
Location: Powell River BC Canada
Leigh wrote:
radiotechnician wrote:
The DC resistance is of concern, It sets the DC current in the 125 transformer. It must
not exceed this because it will overheat, while waiting for some program to produce AC watts.
The 125 D is rated at 70 mA DC.
Huh?
The plate current is set by the element voltages.

The reflected impedance of the speaker through the transformer sets the dynamic load, not the Ib.

Transformer current ratings are maximum permissible, unrelated to tube operation.

- Leigh


The DC resistance is what determines the current in the circuit as far as the transformer is
concerned. If exceeded overheating will occur. Tube operation is one of the factors that can
cause the DC current to be exceeded. Apart from shorted or leaky components, the possibility
of a wrong tube in a socket could be the reason. The bottom line, (as in this question about
using other than original parts) When sets were tested, all probable factor were introduced,
and they simply watched what happened. If it caught fire or dripped burning insulation it
didn't pass.

Here is part of standard in place when I was working with the agency getting our stuff approved.

Attachment:
Safety tests.jpg
Safety tests.jpg [ 133.77 KiB | Viewed 2489 times ]

_________________
de
VE7ASO VE7ZSO
Amateur Radio Literacy Club. May we help you read better.
Steve Dow
ve7aso@rac.ca


Top
 Profile  
 
Post New Topic Post Reply  [ 158 posts ]  Moderators: Marcc, Norm Leal Go to page 1, 2, 3, 4, 5 ... 8  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: Majestic-12 [Bot] and 10 guests



Search for:
Jump to:  




























Privacy Policy :: Powered by phpBB