Valiant driver transformer

[W9BHI]

Has anyone ever had to replace the audio driver transformer in their Valiant?
I see that Hammond makes a few that some say have better response.
They are models 124D and the 124E.
Which one should be used?
Thanks,
Don W9BHI

[W3FJJ]

Hi Don, I tried replacing my with a 124E, i believe, not that is the correct one, Im not sure. But I'll just
report my findings. Before I replaced it, I did a freq sweep  with scope on grid of modulator, with  original valiant xfrm. It  was
lacking bass response. I then did a sweep of hammond transformer, with no DC on it just a load, and looked great.
I put it in the circuit and did sweep, and it lacked bass just like valiant original. I concluded, neither transformer
liked the DC on it,, and possibly saturated the core.. I herd people using a choke and AC couple driver transformer, and supposed to help.
I would of liked of tried that, but I wound up doing a phase splitter circuit and eliminated the driver xfrmer all together..

GL, Chuck-W3FJJ

Has anyone ever had to replace the audio driver transformer in their Valiant?
I see that Hammond makes a few that some say have better response.
They are models 124D and the 124E.
Which one should be used?
Thanks,
Don W9BHI

[W9BHI]

I came across this schematic of an audio mod for the Johnson Viking.
It shows a cap in the circuit that keeps dc current from flowing in the primary of the transformer.
Maybe this would help the low frequency response.
Could this be adapted to the Valiant?

Don W9BHI

[W9BHI]

I meant to only show the one mod but it shows the whole file.
Sorry about that.
Don W9BHI

[ke7trp]

Don. Which cap is it and which schematic?  Lots of neat info in that pdf.  I think that the cap on the primary was used in a recent electric radio article.. Its the one where the guy builds the modulator for the HALF viking.  He also used a 15K 4 or 5 watt resistor to shunt the transformer and got a big boost is low end... I have to dig out the copy of electric radio..

C

[Steve - K4HX]

Just trace the lead from the plate of the new 6AQ5 driver tube to to the driver transformer. You'll find the cap. This is  good mod since it will improve low end response and reduce the likelihood of saturation and the associated distortion.

The cooling mods are interesting. I used a fan on my Viking II even without any power increase.

[Rob K2CU]

On the topic of Valiant transformers, has anyone ever measured the inductance of the primary and secondary windings of the driver and modulation transformers, or know where the spec's are listed? I have winding resistances from the manuals.

ALso, I had created a simple relay sequencer circuit when I added an antenna relay to the rig. What is the best way to post it? It is presently a Visio drawing.

[KE6DF]

ALso, I had created a simple relay sequencer circuit when I added an antenna relay to the rig. What is the best way to post it? It is presently a Visio drawing.

You could post it as a PDF file.

You can download freeware PDF print drivers. Once installed, they look like another printer on the pull down list for selecting printers when you go to print the Visio file. They prompt for a file name and create a PDF instead of actually printing anything.

Or, if Visio allows, you can save the drawing as a JPG file and then attach that to your post.

Very easy unless  you file is bigger than 5MB -- which it probably will be. If bigger, you need to break it up into multiple attachments which is a PITA but can be done.

[Rob K2CU]

Just needed to know what format.
Valiant Transmit antenna and power sequencer.

PTT --> antenna switch and rcvr mute-->delay --> apply power to TX.
release -->depower TX-->delay-->switch ant and rcvr unmuted.

using other relays may require adjustment in delay component values.

These relays were selected as they have convenient mounting tabs to mount in chassis. I may have pix for those interested. I think one terminal strip (chicken on the fence type) was used as well as soldering to relay tabs. Antenna relay
mounted on rear apron next to coax jacks....added one BNC for rcvr antenna. Other relay mounted on side apron near rectifiers. Can take pix as I am planning to open rig to do some audio testing.

[W9BHI]

Very nice circuit.
I used the same relay but 4PDT in my Ranger II.
It fit nicely under the chassis.
I also used the same voltage doubler circuit.
The voltage was a little bit high(14.5)when the relay was keyed, so I put a 13 ohm 1 watt resistor in series to bring the voltage down to 12.2 volts.
Maybe it's lower on your cicuit because you're using 2 relays.

Don W9BHI

[Rob K2CU]

IF you're just using one relay, then simply reduce the voltage doubler caps to something smaller, like 470uF.