Mastech HY1803D Transformer - Page 1
Forum section: electronics / repair

author: kickit2
author_rank: Contributor
timestamp: August 27, 2015, 01:41:43 am
content: Hello everyone,Quick question - need a new transformer for my HY1803D - mine has shorted and of course doesn't work so well in that state. Anyone know what a comparable replacement would be, or at least what the VA ratings need to be for the multiple different outputs?Thanks

author: MarkF
author_rank: Super Contributor
timestamp: August 27, 2015, 02:56:33 am
content: Is this the supply you have?Mastech HY1803D Variable Linear DC Power SupplyAt $40, it may just be easier to get a used one for parts.

author: mij59
author_rank: Frequent Contributor
timestamp: August 27, 2015, 05:53:10 am
content: Transformers are very robust, are you sure the transformer has shorted ?Using spare parts would be a good option since its a custom made transformer, using standard available transformers you will need something like a 2*12V 4VA transformerand a 2*12V 100VA transformer.Or you could replace the faulty winding of the transformer, anyway new power supply may be cheaper.

author: krish2487
author_rank: Frequent Contributor
timestamp: August 27, 2015, 06:57:50 am
content: To add to what mij59 has written,If you try to measure resistance or continuity using a multimeter on any one side (i.e primary or secondary) , you will ALWAYS read a dead short.In case of transformers, the only short you should worry about is between primary to secondary. If you read a short between any winding on the secondary to any winding on the primary, you have a problem.However, transformers are VERY robust as mentioned. In all my 6 years of working in power electronics industry, The only time I have seen a transformer get damaged is due to a fire.

author: kickit2
author_rank: Contributor
timestamp: August 27, 2015, 10:54:11 am
content: Yeah - the unit overheated and the transformer partially melted. Now I only get ~2v out of the one winding, and she gets dangerously hot and stinks after 30 seconds or so, even with the transformer not connected to any load. So I'd say it's bad.I looked at a new supply, but thought I'd evaluate repairing it first - although the thought of a used one is a good alternative.I use it to charge my kids three power wheels that don't have chargers, and I'm thinking I should add some cooling fans on this in either case for te future.Thanks

author: tooki
author_rank: Super Contributor
timestamp: August 28, 2015, 09:47:54 am
content: Power Wheels use big lead acid batteries right? Why not buy a proper charger instead? They're not that expensive.

author: rvalente
author_rank: Frequent Contributor
timestamp: August 28, 2015, 07:35:23 pm
content: Since you leave in the USA, there is no better country to score cheap T&M equipment, I'd suggest to look for some old HP 628x units in ebay or craiglist, I own the 6289A and it is such a nice supply!Give up of the shit chinese power supply, the vintage 60...70... 80's are so much better and cheaper!

author: Seekonk
author_rank: Super Contributor
timestamp: August 29, 2015, 08:35:06 pm
content: I bought one of these defective on ebay for $15. The transformer had come loose and tore off the wire on the transformer that powered the meter. I located a schematic on the internet from Russia, no offense, but I downloaded the pdf schematic and printed it out at the library. Here is what I remember. A 12V transformer should work for you. They use a tapped winding, like 12 and 16V, a relay switches the winding depending on what the voltage is set at. If just charging batteries you could probably tie those two together. A small electronic wall wart could supply the isolated meter. You won't find a single transformer that supplies everything you need but the case has enough space to fit a couple transformers in.