90 volt battery eliminator

[Yorkie]

Nixie clokc PSU is interesting, and obviously has potential as a self-contained battery powered HT/LT unit for a battery valve radio. I'm not familiar with the Max1771 IC of the IRF 720, but I assume that as with most designs which lift LT to HT, it's some form of oscillator. Most such circuits suffer from whine which is audible on the radio - I wonder if this design does? That wouldn't be an issue for its intended purpose - as a nixi clock PSU, but would limit its usefulness as a batter radio PSU.

Anyone tried one out yet?

David

[tiv48]

hi yorkie. this comes as a ready built modual .changing r1 to 470k gives 70 volt output with a 4.5 volt input see pics of my earlyer post in this thread . i have had it running a vidor 434 for 6 hours ,no hash or other nasties . the first one i tried about 4 years ago was hopeless built arond a 555 and a transformer. thease new ones from ebay Item number: 250747824418 cost only £10.95 +£1.59 postage and as i said before battery pack and modual will fit inside a b126 battery case with plenty of room to spare
the same cant be said for 10 pp3s .i am going to try and use one to make a safe cap reformer next
cheers rob t

[Yorkie]

Thanks for the feedback Rob - sounds excellent - the best solution yet, provided the current capacity is sufficient for whatever set it's desired to use it for. I guess it would be no problem with the low consumption DKxxx DFxxx series of B7G valves. Chep enough too - as you say, as cheap as a stack of PP3s of dubious capacity from the pound-shops.

David

[tiv48]

rated output at 120 volt is 250ma no probs running the vidor witch takes (i think)just over 110ma
i was amazed how well it worked,i have asked on other forums about running these portables. if i was as good as mike cummings at stuffing batteries i would never hae found this solution
rob t

[Mark R]

Guys
Tony has supplied me with the schematic and some thoughts for his design, which I intend to build (parts obtained).
Tony mentioned in his emails that the voltage reg runs hot. So some thoughts for Tony.....
1 I intend to put a volt meter in the LT supply to read the voltage output so the filament voltage can be varied, depending on the set.
2 If the filament voltage is raised the heat will be greater.

so, If I put a big heat sink on and use a switched 240v cooling fan in a large case which is ventilated.

Question is do I need the cooling fan?

cheers Mark

[Aerodyne]

Mark
The heat generated will be much the same regardless of the voltage setting, so as long as you work within the regulator's limits there should be no need for additional cooling. All such regulators run hot, most have a built-in thermal regulation circuit and will shut down if overloaded (but check on this). It is also possible to run two regulators in parallel, I believe. The data is available by download, google search needed.
-Tony

[Aerodyne]

[attachment=1009]It has been pointed out to me that the diagram I posted for the simple power supply has an error, in that the diodes are the wrong way around in the bridge. This happened during the conversion from schematic to jpg but quite how is beyond me, though I should have spotted it - and another silly error in the suggested component layout as published in RB issue 124. I'm grateful to 'Radioman' for alerting me to the diode problem and have sent a letter to RB suggesting a correction be published in feedback.
I have also attempted to add the corrected diagram here.
-Tony

[Shaman]

Hi, i bought an old Ekco, eliminator, 90 volt 120 volt, The lt section i do not use as i find dry cells give, a brilliant hum free operation with this unit, its got to have been made in the 30,s, but runs spot on, regards.............Alan

[tiv48]

if you have an old ht battery , remove the cells but leave the conector block and i will re build it to take 3/4 aa batteries for £15 including postage
rob t