Satellite receiver - no +5 V SB

[Behemot]

An attempt to repair this one has been made but it still does not work. There is TNY267PN PWM controller with integrated MOSFET. Seems that it has exploded. It was replaced together with (probably) the optocoupler, some diodes and caps. According to O-scope it is not working as I only see 50Hz input capacitor ripple on the transformer primary (and secondary).

I read something over 5 V on the C10 capacitor right next to the TNY267PN. There is 1,43 V over PC2 optocoupler and also the EN/UV pin of the TBY267PN.

Any idea? Is the PWM bad again? Or wrong optocoupler has been selected?

[stj]

Re: Satellite receiver - no +5 V SB

capacitor ripple?

if you have no load, you shouldnt have any ripple - that's why the cap is there.
i'd check the primary smoothing cap first.
one other thing,
unless one of the rectifier diodes is dead your ripple should be 100Hz if it's full-wave rectified!

[Behemot]

Re: Satellite receiver - no +5 V SB

The cap in question is Samyoung 68 uF/450 V, measures 77,6 uF and 0,57 ohm.

I should notice I did not have the negative side of the capacitor grounded by O-scopes ground and the PSU itself only has phase and neutral so it may have been floating a bit, as the waveform looked almost as one half of sine wave. The point is, the TNY267PN is not switching.

[stj]

Re: Satellite receiver - no +5 V SB

is there any short on the output side of the transformer?
and is the transformer open-circuit?

i'm still not happy that your seeing ripple on what should be a DC line.
if you see ripple now, what the hell will it look like when the main switcher starts creating a load!

[budm]

Re: Satellite receiver - no +5 V SB

The scope probe ground has to be on the Negative leg of the cap because that is the circuit ground ref, if you do not put the Ground probe there then you will see big way form because the bridge is the isolation (not electrical isolation) between the Line and Neutral of the incoming AC. You will have to put the load on isolation transformer that has both Line and Neutral floated by not the safety ground to allow you to put scope ground on the negative legs of the cap.

What is the original opto # and the sub?
D18 Protection diode is OK (it does not it was replaced?

"some diodes and caps" which one?

[Behemot]

Re: Satellite receiver - no +5 V SB

Every isolation transformer has line/neutral floating, that's the principle isn't it? Here it is easier as the supply does not use ground…

Anyway, I am afraid I did not get the original optocoupler but there is another one for main supply feedback, we can maybe anticipate both were the same from factory…?

[budm]

Re: Satellite receiver - no +5 V SB

Not all, that is why you have to verify, some will have Neutral tie to ground. I will not assume, I check it first.
https://cdn.badcaps-static.com/pdfs/...1f890bb7fa.pdf,

BTW, I have this TRIPPLITE from the customer, that one of the DIY repair guy bought it thinking that it will be safe to use, but guess what, I check it and open it to show him what inside the unit. He blew his scope and his power supply board he was trying to fix even. I warn him to check that isolation transformer first but he did not listen, he told me the people on the web use then so it should be OK.

You can also see that if it is Iso ground, the outlet would be Orange color for Iso-Ground outlet:

You need to look at the spec of the two opto to find CTR spec.

[Behemot]

Re: Satellite receiver - no +5 V SB

I see. Well I have connected that myself, got that 2kVA transformer if mine without any cabling. Only the core is grounded.

[budm]

Re: Satellite receiver - no +5 V SB

I built my own too so I know it is made correctly.

[Behemot]

Re: Satellite receiver - no +5 V SB

Yeah I checked and really only the ground pin is grounded

As for the stand-by transformer, well, it seems OK optically. All three windigs are conductive but that's about it, it has so low inductance I cannot measure anything with CT-Micro, only some small resistance there.

[budm]

Re: Satellite receiver - no +5 V SB

Never mind, wrong post.

[kasfamily]

Re: Satellite receiver - no +5 V SB

replace IC4

[Behemot]

Re: Satellite receiver - no +5 V SB

Is it the TNY267PN? I don't have the board right here…

[kasfamily]

Re: Satellite receiver - no +5 V SB

Is it the TNY267PN? I don't have the board right here…

Not. IC4 is that of a series of 431, and is on the board shown in the secondary (cold) chain optocoupler.

[Behemot]

Re: Satellite receiver - no +5 V SB

Oh I see, TL431. Can try.

[Agent24]

Re: Satellite receiver - no +5 V SB

There are some good example circuits in the datasheet including opto part numbers that might be suitable.

[Khron]

Re: Satellite receiver - no +5 V SB

I second the idea of checking the mains rectifier bridge / diodes.

Also, it might be worth checking if the snubber components are all (still) ok. Usually it's an RCD snubber across the (main) primary winding of the transformer.

In this case, they're most likely the ones between the TNY267 and the transformer. I hope / assume that charred resistor(?) in the 3rd photo has been replaced?

[Behemot]

Re: Satellite receiver - no +5 V SB

Two diodes were repalced incl. the snubber.

I may replace the resistor in there, it reads 15 ohm and should be 22, even though I don't think that is that much of a difference…or is it?

[Agent24]

Re: Satellite receiver - no +5 V SB

Hard to say. Is it within its specified tolerance? If not, definitely replace it.

[Behemot]

Re: Satellite receiver - no +5 V SB

I've replaced the TL431, no change. The resistor is now within tollerance, don't know what happened.

What are the important characteristics of an optocoupler? TNY datasheet specifies LTV-817 or TLP181Y in sample circuits, the ones in here (seems like replaced) are 817B, possibly FOD817B. This has CTR of 130-260 % while TLP181Y has 50-150 %. LTV-817 is not known, in the sample circuit there is no class specified.