UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Amateur and Military Radio

Notices

Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

Closed Thread
 
Thread Tools
Old 28th Jan 2014, 3:01 pm   #1
smirnisio
Retired Dormant Member
 
Join Date: Mar 2012
Location: Greece ,Athens
Posts: 16
Default Help!How to replace an Electromagnetic speaker with a Pm one?

Hello ,
I recently owned a Rca radio in bad condition and without a speaker.

I have recapped it but the electromagnetic speaker and the output transformer is missing.I have read about changing the transformer with a filter choke or a resistor but I am a little bit confused about the real values I must put on or how to connect them.
The radio is RCA Q122 as you can see in the schematic. It has two 6f6 output tubes with a 10Kohm plate to plate load resistance.

I also have a spare output transistor that has primary resistance of 450 ohms and secondary 1.5 ohm. Can I use it somehow?
Any suggestions will be appreciated!

Thank you in advance
Attached Files
File Type: pdf usa%5Frca%5Fq122%5Fq122x%5Fsch1%2Epdf.pdf (297.4 KB, 121 views)
smirnisio is offline  
Old 28th Jan 2014, 3:26 pm   #2
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
Default Re: Help!How to replace an Electromagnetic speaker with a Pm one?

For the output transformer - you need a standard "Push-pull" valve output transformer - have a look here: http://www.hammondmfg.com/1608A.htm I'm thinking the 1609A would do just fine.

The original speaker's field-coil is also the smoothing choke - the item marked as "FIELD" connected to the right of the 5Y3-GT rectifier tube. For this you need a 10-Henry choke - I'd suggest one rated at 100 milliamps or so. Have a look at

http://www.hammondmfg.com/153.htm where the "158M" looks like it would serve the purpose admirably.

Alternatively you can not use the choke [the circuit in the bottom right corner of the diagram shows how to use a non-field-coil speaker]
G6Tanuki is offline  
Old 30th Jan 2014, 5:44 pm   #3
smirnisio
Retired Dormant Member
 
Join Date: Mar 2012
Location: Greece ,Athens
Posts: 16
Default Re: Help!How to replace an Electromagnetic speaker with a Pm one?

Thank you for your suggestions.
I will put a 5.6 K 10 watt ceramic resistor in the field place!
As for the output transformer I will search here in Greece a suitable substitute.
As you proposed me I should search for a Push Pull 10 Watt output transformer? But at the tube manual for the 6F6 the maximum power output goes up to 10 watt!

smirnisio is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 12:03 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.