Sony regulator question

My shop has seen lots of these caused by bad solder connections at the horizontal drive transformer.

Mark Z.

On a Sony SMPS and horizontal output you absolutely must use exact components. Q601/602 even are of different types and that rating is also very important, mp,mnp,etc.

Given that you shorted some pins together, you may have some other failure now that is putting the loads on the smps way out of tolerance. Might be time to get a hold of Sony's training manual for that chassis and the SMPS training guide given out at school for that SMPS and follow the 18 or so steps to fixing the set.

That won't be enough protection I'm afraid. Using a variac means you can ramp up the voltage slowly, but the current is still potentially destructive if there's a fault. By the time the power supply kicks in and draws excessive current due to a fault, it's all over in a microsecond and your new semicondictors become 'fullyconductors'!

My advice is to use a 100W light bulb in series with the supply to limit the current to safe levels while faultfinding. If it lights brightly and the TV's PSU fails to start, you know there's still a problem and it gives you a second chance to remove the fault.

As you shorted two pins together on the jungle IC, I suspect there's something blown and loading the PSU, possibly the jungle IC itself.

Dave

You should be using original Sony parts. I am sure that the HOT is also damaged. We have had a fair number of cold solder connections at the horizontal scan drive transformer that feeds to the HOT. If the HOT looses proper drive, it can go shorted, and take out the main power supply and a few support components with it.

It is very important to make sure that there are no caps that are off value or high in ESR in the area. It is also possible that the bias resistors in the power supply that bias the switching drivers are off value. It is also possible that the flyback transformer is giving problems.

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JANA _____

First, thankyou to all that replied. Lots of great advice. I am hearing that I definitely should replace with Sony originals. Could this be the sole problem with Q601/602 (NTE subs), disregarding that I caused them to fail originally? I can do the lightbulb trick, but not exactly sure where to insert. If I install in supply, and problem is downstream of this, wouldn't the faulty component still demand the current regardless of this load in the supply? Should I remove the HOT, insert light bulb here, and disconnect the other 135V B+ sources? I just don't want to sacrifice any more components, especially if I buy Sony replacements. I will follow all advice, and post feedback when I get the components in. Thankyou all again.

I'd suggest doing some Googling. These power supplies and this problem have been discussed to death and there is lots of info on them. for the record, Dave, a variac is the better method for these. Most of these supplies will start switching at just a few volts and it is there that you check the duty cycle and the switching frequency. Dave's suggestion to follow the Sony training manual is good advice if you don't understand how they work and fail.

Leonard

Using the Sony supplied parts is bad advice. The original Sony parts will cost many times what you would pay for the same parts from other distributors. The key is to use a higher gain rated version, match the pair, and troubleshoot the rest of the circuit completely. For someone who does not know these supplies, buying Sony part is a great waste of money because they will blow those just as easily as any other parts. Now the NTE subs may be a problem. You never know what they are giving you. Just use a P rank 2SC4834 from a good reliable supplier like B&D, Tritronics, or ACME.

I did extensive testing on these transistors and found (with the help of the suppliers listed) that there was similar variance in the Sony parts as others, in fact more, and that the gain rating mad more difference than what distributor the parts came from. Sony is just another distributor, not the OEM. The notion that Sony has tighter QC or matches the pairs is untrue, as verified by testing on several dozen transistors acquired in batches and at separate times.

I just buy the P rank transistors from the supplier that has them cheapest in batches of 10 and match the pairs. I can buy 10 pieces cheaper than a pair from Sony and get better QC.

It is very rare to have a bad flyback causing these failures, but not unheard of. I had two sets a few years ago that come in within a period of a couple of weeks that made us crazy with these failures and they were finally fixed by replacing the flybacks. I have done many dozens that were just bad connections at the HDT causing the problem.

Leonard