help needed homebrewing a huntron tracker psu. - Page 1
Forum section: electronics / repair

author: m3vuv
author_rank: Super Contributor
timestamp: July 21, 2021, 07:15:54 am
content: hi all,im trying to cobble together a new psu for for my huntron tracker,model htr- 1005B,the 240v primary winding of the psu transformer has gome open,i have a transfo from an old tek scope i can use for most of the voltages ,it has 150v,75v,12v and 6.3 crt heater taps,im stuck trying to find a solution for the -1350v,maybe a motorbike ignition coil?,thought of using a voltage doubler but that will only get 300v,i need 1350,its just the acceleration voltage for the crt so very low current,any ideas how to do it,i would replace the transformer but they havent been made for years,secondhand units for spares are like rocking horse sh1t!,attached a pic of the psu section,thanks in advance.,im just looking for ideas.cheers m3vuv.

author: Just_another_Dave
author_rank: Regular Contributor
timestamp: July 21, 2021, 08:17:46 am
content: Many transformers are designed for a particular product, so finding an off the shelf transformer with a 5.6 turns ratio rated for that particular input voltage might be difficult. Maybe similar products might have a compatible one or you might be able to find it as a 1/5.6 turns ratio transformer rated at least for 1350.On the other hand, although it might not be the easiest solution, it is possible to build a transformer with your bare hands. Cores can be bought from digikey as well as wires and if it doesn’t provide too much power you might not even need simulating it

author: m3vuv
author_rank: Super Contributor
timestamp: July 21, 2021, 08:58:15 am
content: i was looking to find a way of using the tek one i have,cheers anyway.

author: m3vuv
author_rank: Super Contributor
timestamp: July 21, 2021, 09:00:16 am
content: or even using the remains of the huntron with my scope in xy mode somehow?

author: CJay
author_rank: Super Contributor
timestamp: July 21, 2021, 12:24:52 pm
content: The huntron tracker, from memory, is just an octopus tester with a few ranges, trivial to implement.There's also probably no reason you couldn't use a 'tripler' or Cockcroft Walton ladder to generate your 3500V, it won't need an awful lot of current if it's just the CRT anode voltage and would be an awful lot safer than a mains transformer producing that voltage.

author: perieanuo
author_rank: Frequent Contributor
timestamp: July 21, 2021, 12:49:20 pm
content: check first if your transformer has temperature fuse series with primary, should be under the first 1-2 insulation layer.

author: nali
author_rank: Frequent Contributor
timestamp: July 21, 2021, 02:43:26 pm
content: The schematic doesn't show a fuse, but what itdoesshow is an inrush limiting resistor which could be O/C... did you measure the primary resistance across the actual transformer wires or at the mains plug?If the transformer is actually dead you've not got much to lose if you try to remove & rewind the primary, considering it's knackered anyway. See if you can cut it off, count the turns & rewind.

author: Just_another_Dave
author_rank: Regular Contributor
timestamp: July 21, 2021, 08:31:47 pm
content: In transformers with relatively thin wires, they sometimes break or detach from the bobbin due to hot temperatures or vibrations. It’s not the most common failure, but it may be worth checking them as those connections are easy to fix.I don’t know why I thought that you didn’t have the original transformer when I wrote my previous answer, but as Nali said, rewinding it is also a possibility as the core won’t probably be damaged

author: fcb
author_rank: Super Contributor
timestamp: July 21, 2021, 08:37:44 pm
content: Does it have a 110 primary winding? Does that work?

author: fcb
author_rank: Super Contributor
timestamp: July 21, 2021, 08:41:30 pm
content: You can buy a standard LOPT for a small TV for <£10 on eBay.A 555 timer, MOSFET and a LM317T are all you'll need.

author: robert.rozee
author_rank: Frequent Contributor
timestamp: July 21, 2021, 09:49:30 pm
content: how does your unit compare to the one described here:https://isurplus.com.au/manuals/Huntron%20Tracker%201005%20Maintenance%20Manual.pdfthe above already uses a 555 and (similar to a) LOPTy for the -1350v supply, with the mains transformer only generating a single centre-tapped low voltage (regulated to +/-6.0v DC). if not the same as yours, you may still be able to uplift parts of the design to hack together a solution.it would be good if you could post some photos.cheers,rob :-)

author: m3vuv
author_rank: Super Contributor
timestamp: July 22, 2021, 07:13:02 am
content: should of explained a bit more,i built a small inverter 230v to try and run it from 12v as a lot of my work is outdoors,it was trying to mod the case that i managed to slice the transfo with a slitting disk,so its well and truly buggered!,may have a go running the tek 150v tap thru a multiplyer and then a voltage divider to adjust it to -1350v.,this is my one.

author: CJay
author_rank: Super Contributor
timestamp: July 22, 2021, 09:05:33 am
content: The -1350V is not critical , you'd probably be fine with 1250V or 1450V but it does need to be reasonably stable or you may get weird "blooming", image size changes and/or odd brightness changes.It may also work perfectly adequately.Personally I'd probably want to try and sample the 150V out of the transformer to feed it back and control the voltage.The disadvantage of using an FBT is that it will need several KHz drive, the advantage is that they probably come complete with all relevant HV rectifiers, are designed to handle the voltage and likely have more than one winding so you can use one to provide feedback for regulation.If you do try and adjust with a variable resistor try and find a focus assembly from a CRT monitor/TV, that should handle the voltage with ease and save you a load of hassle trying to build something that needs to handle a couple of KV.

author: robert.rozee
author_rank: Frequent Contributor
timestamp: July 22, 2021, 09:27:01 am
content: so it was T3 that you sliced through?i'd be picking up asmall6.3v heater transformer to run the CRT's heater, as that will be handling the bulk of the power requirements. make sure it is good to operate with the secondary sitting 1500v from ground. that just leaves you with the (smaller) problem of generating +340v and -1350v.you can then use the existing drivers (555, Q3, Q4) and a somewhat smaller transformer than the existing T3 that you wind yourself. try and match the number of turns in the existing primary, then add a secondary with an appropriate turns ratio to get up to the 340v. the -1350v is fixed at 4x the 340v by the use of a voltage multiplier, so if the +340v is right then the -1350 will also be correct.cheers,rob :-)

author: m3vuv
author_rank: Super Contributor
timestamp: July 22, 2021, 10:38:30 am
content: sorry i think i uploaded the wrong pdf,heres the correct one!,fingers crossed,btw its tr2 that i killed!.

author: vk6zgo
author_rank: Super Contributor
timestamp: July 22, 2021, 01:50:57 pm
content: Quote from: m3vuv on July 21, 2021, 07:15:54 amBack in the day, I built a TV set which used a 5BP1 CRO tube.This required 2000v EHT, which I obtained with a voltage quadrupler.The original design used 6H6 twin thermionic diodes, but I used OA210 silicon diodes (yes, it was that long ago).I never got the TV going properly, but the EHT "worked a treat!"

author: robert.rozee
author_rank: Frequent Contributor
timestamp: July 22, 2021, 03:07:41 pm
content: upon closer inspection, the manuals you posted (both seem the same) contain two schematics - one on page 12, the other at the end on page 34 (which was the schematic i was looking at).the first schematic is for using a CRT requiring symmetrical deflection plate drive, with a 180v HT supply. this one uses the single, complicated mains transformer that has four secondary windings. the other schematic (at the end) is for using a CRT requiring asymmetrical deflection plate drive, with a 340v HT supply. the power supply (running from a 555) is far simpler, as i described before.likely the two versions simply represent the availability of different CRT supplies at the time of manufacture.before proceeding too much further, it would be helpful to see a photo of the inside of your actual unit, just to be 100% sure which schematic applies. however, even if you are working with the version having the more complicated mains transformer, i think it may still be easier to go for a low-voltage mains transformer, providing 6.3v heaters and regulated +/-6v, followed by a small inverter to generate the HT (+180v) and EHT (-1350v) supplies. as others have commented, neither of these need to be very precise, just well regulated.cheers,rob :-)

author: m3vuv
author_rank: Super Contributor
timestamp: July 22, 2021, 07:26:46 pm
content: cheers rob,yes mine is the one with the complicated transfo,just found this on ebayhttps://www.ebay.co.uk/itm/273949022829,lookslike it may be ok for the eht?,cheers Paul.