Chroma 6530 AC Power source teardown / repair - Page 1
Forum section: electronics / testgear

author: dxl
author_rank: Regular Contributor
timestamp: April 22, 2022, 08:02:41 am
content: I noticed a Chroma 6530 AC Power source on ebay for 450 EUR. Initially i sent a lowball offer, but in the end i couldn't resist just buying it for 450 EUR. I always wanted to have an AC power source, but usually they are pretty expensive. So i would have been mad at me if someone else would have bought it while i was waiting for the seller to accept the offer.The specs are impressive: 0-300V, 15A or 0-150V with 30 Amps. Frequency range is 15hz to 2Khz. This beast is big and heavy, a bit bigger than i wanted.Now the bad thing: This unit was sold as broken, so i have to repair it first. When i received the unit i heard a lot of rattling noises from the inside, and was expecting the worst. But luckily the former owner just tried to repair it, and didn't put it together. He just threw in all the pcbs and screws...That's why you always should do a visual inspection before turning it on.I then put everything together, and figured out that the small power supply on the M1 board is broken. The UC3844 has around 30 Ohms between Vcc and GND which is clearly an indication that it's broken. So i ordered that part, and now i'm waiting for the replacement to arrive.The Output section and High power parts are looking ok, so i hope that they are working. The only thing i don't know is how the wires are connected to the Output (O) Board. If someone else has such a unit or information how the cables between the boards are connected that would be awesome. I haven't found a teardown of this unit, so i thought while waiting for the spare part i take a few pictures of the Boards.

author: dxl
author_rank: Regular Contributor
timestamp: April 22, 2022, 08:15:59 am
content: More pictures:

author: dxl
author_rank: Regular Contributor
timestamp: April 23, 2022, 05:57:55 pm
content: Slowly making progress, the small power suppply is working now, but unit now complains with 'INP int', which according to the user manual means input voltage to low...

author: f14
author_rank: Regular Contributor
timestamp: April 26, 2022, 09:34:25 am
content: look the paper sticker seem this 6530 make in year ~1996 or 1998 ?

author: dxl
author_rank: Regular Contributor
timestamp: April 26, 2022, 06:01:33 pm
content: Quote from: f14 on April 26, 2022, 09:34:25 amYes, most of the semiconductors have 95/96 datacodes, so likely that this unit was sold somewhere around late 96 or 1997. I wonder how old the design is, given that it's all through hole technology and that it has an 80188 Processor.But might be not so old, i think the 80188 CPUs were product until the late 2000s...

author: dxl
author_rank: Regular Contributor
timestamp: April 29, 2022, 06:03:58 pm
content: She's running againThe display has a really bad viewing angle - but otherwise seems to be a great unit. So basically i had to change all semiconductors that are connected to the +12V power supply on the primary side, which are:On the I board: (Power factor correction)1x LM3391x CD40111x CD40811x ML4812M1 "small" power supply1x UC38441x 78121x 2N67281x 1N41481x 1N4007ADAUX relais driver:2x 2SK975... And two copper traces on the M1 board vanished. So i'm not sure whether that was caused by some lightning strike.But still, except for the ML4812 no fancy parts that couldn't be obtained. The ML4812 was a bit more expensive, i had to order it in UK which summed up to about 20US$. But 20US$ is of course not much for this type of test gear. After finishing the repair i was afraid of connecting all the power PCB's together and turning it on (i was expecting a big "boom" sound)During my repair i drew schematics from the I,G and ADAUX board. The G board isn't complete, but maybe this is helpful to someone someday.

author: nctnico
author_rank: Super Contributor
timestamp: April 29, 2022, 07:06:28 pm
content: Maybe add a 12V TVS to the 12V power supply. If it fails again for some reason, then you won't need to replace all components connected to 12V.

author: dxl
author_rank: Regular Contributor
timestamp: April 29, 2022, 07:24:15 pm
content: 12V wouldn't work - it's much higher (~25V) on startup. The reason for that is that the ML4812 has a Vcc threshold - it's starts at 16V, and stops at 10V. So what they are doing is that they short-circuit the 7812 on startup with a transistor. After about 2s this transistor opens, and the 7812 will be in charge of regulating the 12V. I could of course add a protection diode with 30V or so.