[Amps] Buck-boost xfmr

[amsctalx at comcast.net]

I've never seen, or heard of, the primary supply section in the power supply fail - for any reason. The problem with the supplies is that there is an approximately 12V "sub-supply" that feeds the control subsystem (to provide remote on/off control from Yaesu transceivers) that is regulated and protected through three "fuse resistors". These will, by design, fail if exposed to excessive voltage, are a gigantic pain to find today and will prevent the amp from working if they open. They're not so much sensitive to sustained voltage near the published limits as they are transients, which cause them (by design) to open, thus preventing the entire amp from operating. 

I ultimately ended up buying a surplus marine AC line conditioner to protect everything in my shack from the lousy power from our utility company. I only had this occur once to me, but this "sub-supply" is a glaring design compromise and needs to be protected. It's a gigantic pain to disassemble the "origami" PS internal enclousure and board assemblies, and about a $500 repair to send to Yaesu. 

Again...the thing to protect against are transients. 

73, 

Mike - N8MSA 

----- Original Message -----

From: "Jim Thomson" <jim.thom at telus.net> 
To: amps at contesting.com 
Sent: Thursday, June 26, 2014 6:32:43 AM 
Subject: [Amps] Buck-boost xfmr 

Date: Wed, 25 Jun 2014 21:41:36 +0100 
From: David Lisney <g0fvt at hotmail.com> 
To: "amps at contesting.com" <amps at contesting.com> 


Hi, the power supply for the Quadra is a switch-mode, the manual seems to reckon 240v is ok. 
In the UK our mains voltage is 240v, as far as I know Quadras survive that fine... I personally would run it straight off your mains supply... the buck transformer is a valid approach to sorting out the supply voltage issue... however it is vital that current is not allowed to pass through the low voltage secondary without the primary powered. 
A 15v 10a transformer should do the job... 
regards David G0FVT 

## I see no reason why a 10-15v @ 15A CCS xfmr cant be used.... with NO 120 vac applied to the 120 vac primary of the buck-boost xfmr. All that would happen is you wont get any boost-buck action. 
If you really want to get fancy, you can always install a small 0-120 vac variac, say a 2A CCS variac, on the primary side of the buck-boost xfmr..and vary the amount of buck-boost you want... from 0-15 vac in this case. 

## Having said all that, has anybody actually blown a Quadra up.....from line V being too high ??? I could see transients-spikes-surges etc, blowing it up.... but that is something that could be averted with movs at the main 200A panel etc. 

## Interesting to note that the old Q manual sez its rated up to 234v. New manual sez its rated to 240 vac. Wonder if they just changed the manual ? 

## If you folks do try a buck-boost xfmr, make damn sure its wired for buck..and NOT boost... or you will be in for a rude awakening. Test the xfmr out on a 100 watt light bulb 1st... + DVM. 
## Does yaesu still make the quadra ? I see Acom has its 600 w SS amp in production....which will handle just about any line V you can throw at it. It also has power factor correction built into it. But at $3K a copy, I think I will pass on it..esp with the lousy IMD. 

Jim VE7RF 


_______________________________________________ 
Amps mailing list 
Amps at contesting.com 
http://lists.contesting.com/mailman/listinfo/amps