Radioshack Relay Transformers

[dreric]

I'm starting two builds and i just noticed that the radio shack relay transformers have a center tapped secondary. On the shematic there is no CT shown so my question is:

CT = tied off
or
CT = to ground

Thanks

Eric

[jborders5]

tied off

[dreric]

Thank you!

[talbany]

Dreric..

FWIW.. Both Full wave bridge and Voltage doublers don't require a ground reference CT..As a Warning!!.If you do ground a CT on a FWB count to 30 then buy a new transformer..
A grounded CT is required when using a full wave rectifier..

Another FWIW..Both FWB and voltage doublers are known for being very quiet which is why I believe Dumble used them for the relays..less chance for noise there IMO..However they will run hotter..

Hope this helps!!

Tony

[dreric]

I'm unclear on the voltage double thing. Is the relay circuit in the 124 the doubler circuit? Or is the circuit in the HRM 101 the doubler? Either way I don't understand how the voltage is getting doubled.

Thanks

Eric

[67plexi]

Eric, This should clear things up. http://www.play-hookey.com/ac_theory/ps ... liers.html
Also The new book Designing Power Supplies for Tube Amplifiers ,Merlin Blencowe.
Is a good one and covers voltage multipliers.

Steve.

[talbany]

Dreric
You can also download the Duncan Power supply designer..Lets you input different rectifier configurations showing schematics w/voltages of your design..

124 uses a voltage doubler.. Not sure of ODS 101 HRM.. My schematic of this does not show the PS for the relays..if you don't want to use the doubler you can wire it like 183/Bluesmaster..Below FWB

Good Luck!!


http://www.duncanamps.com/psud2/index.html

Tony

[CHIP]

AFAIK, The set up on the #124 layout is a Voltage doubler ,the relay power supply on the #183 is a Full wave bridge.

little late on the response.

[mlp-mx6]

What transformer did you buy? 12.6V? If so, you want the bridge rectifier. If the 6.3V, doubler.

[dreric]

What transformer did you buy? 12.6V? If so, you want the bridge rectifier. If the 6.3V, doubler.

I have the 12.6V.

I started two builds of different eras so I could learn about the differences as I build through. I am building a 102 / Ford and a HRM Bluesmaster w/ EL34s, (or at least trying to).

My understanding of the relay voltages was that it depended on what the voltage requirements the relays wanted. Or did HAD always use 12v relays?

Conceptually:

For the Bluesmaster w/ bridge:

12v AC to rectifier becomes 12v DC into 12 volt relays

For the 102: w/ voltage doubler:

secondaries @ 6v AC into doubler and rectifier becomes 12 v DC into 12 volt relays

Please let me know if my logic is wrong, looks like I need a 6 volt transformer! If this is so, where do people get the 6v transformers? Radioshack doesn't seem to have them anymore.

Thanks

Eric

[guitardude57]

The 12V 450mA RS tranny ........rectified.... no center tap, I get around 16.7 volts from the bridge to the 12V regulator.

Then 11.92 volts out to the relay, on my build.

Just a 6-0-6 transformer.............5 bucks I think I paid for it.

[67plexi]

Eric, Radio shack has no 12v transformer in my town.
This is what I used. TRF-110 3-0-3 volt = 6 volt @ 1.5A. TRF-120 6-0-6 volt = 12 volt @ 500 mA.
http://www.abra-electronics.com/product ... rmers.html
TRF-110 used a 7805 voltage regulator for 5 vdc. W/ Jasons HRM board and bias/relay board.
TRF-120 used a 7812 voltage regulator for 12 vdc. W/ NTE # R-40-11D2-12. Relay.

Take care, Steve.