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Old 18th Feb 2017, 3:28 pm   #41
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Default Re: Sony HP-511 - Blowing Fuses

Just a very quick look, a BD241C looks promising as does a TIP31A both about 50p each from Farnell.
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Old 18th Feb 2017, 4:07 pm   #42
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Default Re: Sony HP-511 - Blowing Fuses

Thanks Julie...

Forgot to reply to your previous question regarding Hi-Pot's? The amp board doesn't have any hi-pot's but the MPX board does have several. I'm feeling as though I should leave the pot's well alone at the minute with my very limited understanding of what I'm doing with the amp board... At least there are some alternative Q's available, even if it requires some plier 'tweaking'"!

I did find this Q, Bux77 TO66

http://www.ebay.co.uk/itm/BUX77-POWE...25.m3641.l6368

and a spec sheet on the Q, which seems to roughly match the dimensions of the originals. 5A 40watt? £3.50 delivered seems like a reasonable option if it's more 'plug and play' so to speak.

http://products.semelab-tt.com/pdf/bipolar/BUX77.pdf

Would a 5A transistor cause issues?
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Old 18th Feb 2017, 4:08 pm   #43
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Default Re: Sony HP-511 - Blowing Fuses

TIP31 springs to mind, though it seems a bit weak gain-wise. That wouldn't be enough to put me off from at least trying a couple, though, since they're cheap (five for £2 including postage) and gain figures in datasheets often tend to err a bit on the pessimistic side. The A, B and C suffixes refer to 60, 80 and 100 volt variants; but the original transistors were only rated for 40 V, so any will do.

If anyone can suggest a similar device with a bit more hFE and not much more expensive, feel free to use that .....

You will also need to replace the speaker coupling electrolytic capacitor, and it would be prudent to test the speaker with an alternative music source too. If that was what killed the output transistors, it might also have done the speaker in; potentially setting you off chasing a non-existent fault, when the repaired amplifier sounds distorted because the speaker you were listening through is faulty. (Been there .....)

EDIT: The BUX77 looks like a suitable replacement. It will withstand a higher voltage and current (which is no problem) and has a slightly higher gain. Bear in mind, though, this is still going to be a smoke test .....
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Old 19th Feb 2017, 7:36 am   #44
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Default Re: Sony HP-511 - Blowing Fuses

Yep, the BUX77 will fit right in, same pinout, well done for finding them. Might be worth getting four. I'd still try using a couple of TIP31's first to make sure all is well though.

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Old 22nd Feb 2017, 11:10 pm   #45
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Default Re: Sony HP-511 - Blowing Fuses

Perfect, thank you...

I have purchased 4 TO220's to test.

I also desoldered the 2200uf capacitors from the amp board and tested them on a capacitance meter. On the 20mF setting, the capacitors read 2.47 and 2.50. These readings appear to be within range? I tested the smoothing capacitor too and this came back with a reading of 2.55. Resistance reads using DMM 200k Ohms were similar to the smoothing capacitor also

If these readings are ok, is there any other reason that the OP's have failed? Is it possible that the OP's went due to age?

I will check the driver transistors when I find some more free time.

Last edited by gazrawly; 22nd Feb 2017 at 11:17 pm.
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Old 23rd Feb 2017, 5:51 am   #46
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Default Re: Sony HP-511 - Blowing Fuses

The capacitors might read within spec ( 2200u +/- 20%) but it isn't a good indication of health. A capacitor
can have a high equivalent series resistance (ESR) to AC as well as being leaky, IE it doesn't block DC and leaks current. It can leak gunk (electrolytic) too.

An ESR meter can check ESR but to check leakage you need to apply a cap's working voltage, put an ammeter in series with it or some other indicator.

It gets more complicated still, caps can be reformed or just replaced on sight. Usually though big smoothing caps like yours are OK, it's the little ones that can cause the trouble.

What caused your amp to die? Could be one or more causes out of 100's of possibles, finding it takes experience and knowledge. Changing parts doesn't always work, you have to know what's going on. In your case though that's all you can really do. Replace the cap on the output as well as the smoothing caps while you're at it replace the blown trannies and check drivers. Start up on a Lamp Limiter and pray.

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Old 28th Feb 2017, 8:35 pm   #47
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Default Re: Sony HP-511 - Blowing Fuses

Thanks Andy.

I am about to order the capacitors from CPC and am trying to source two driver transistors (2SA706 and 2SC1124). The original transistor specifications are;

706 (PNP);
Uce/Ucb: -40/-40V
Ic: -1A
β (Ic/Ib): -
N: 7.9W
F: 120MHz
Tmax: -

1124 (NPN);
Uce/Ucb: 140/140V
Ic: 1A
β (Ic/Ib): -
N: 7.9W
F: 120MHz
Tmax: -

When it comes to specification, do they need to be 120Mhz, 8W, 1A? Or could figures be greater/smaller? I have tried to source originals but they seem to be quite expensive (£15 each). I am having trouble finding anything with a 120Mhz frequency rating... There are similar transistors with a 50Mhz rating?

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Old 1st Mar 2017, 6:36 am   #48
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Default Re: Sony HP-511 - Blowing Fuses

Are the driver Q's definitely dead? I'm no expert on transistors, hopefully someone will be able to advise a replacement. But see here - https://english.electronica-pt.com/c...nce?ref=2SA706 and here - https://english.electronica-pt.com/c...ce?ref=2SC1124 Also check out NTE - http://www.nteinc.com/ they have replacements IE NTE211 and NTE190. I'll have a look in my stash, I may have one.

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Old 1st Mar 2017, 10:13 pm   #49
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Default Re: Sony HP-511 - Blowing Fuses

Thanks Andy, I will take a look....

The 706 has definitely shorted but the 1124 tests ok to be fair. I just thought it would be a good idea to replace both since the board was exposed?

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Old 2nd Mar 2017, 6:40 am   #50
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Default Re: Sony HP-511 - Blowing Fuses

Yes, you might as well replace both and get a few spares if your going to keep this deck.

I was out yesterday, will try and remember to look today.

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Old 5th Mar 2017, 3:13 pm   #51
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Default Re: Sony HP-511 - Blowing Fuses

Thanks for your help again...

The NTE replacements seem to be around $14 each plus postage... The pinout appears to be different - I'm guessing I would have to twist the legs to correct the pinout onto the board?

I did find this transistor, it seems to be the correct specification for the 706 (although incorrect pinout again)
http://www.weisd.com/test/GenericPar...itid1=2SA1592R

It is a 2SA1592R and appear to be £1.60 each. The spec;

Type Designator: 2SA1592R

Material of transistor: Si

Polarity: PNP

Maximum collector power dissipation (Pc), W: 10

Maximum collector-base voltage |Ucb|, V: 120

Maximum collector-emitter voltage |Uce|, V: 100

Maximum emitter-base voltage |Ueb|, V: 6

Maximum collector current |Ic max|, A: 1

Maksimalna temperatura (Tj), °C: 150

Transition frequency (ft), MHz: 120

Collector capacitance (Cc), pF: 13

Forward current transfer ratio (hFE), min: 100

Noise Figure, dB: -

Package of 2SA1592R transistor: TO202
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Old 2nd Apr 2017, 7:37 pm   #52
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Exclamation It all ended with a bang...

Albeit a very little bang

The unit is a HP-511a and originally was blowing a couple of glass fuses. 2 OP Q's were blown alone with a driver Q. I've replaced both OP Q's and both driver Q's. I also replaced both Capacitors too (2200uf).

After this, I ran the unit on an LL and it seems to be operating for some 4 hours perfectly on the left channel. There was some crackling coming from the right channel but there was audio from that channel. I put this down to the spade connectors on the RCA outputs as if I wiggled the wires, the crackle would change/clear.

After around 4 hours of the unit running on the LL, I plugged the system into the wall, hit the power switch and had a dull humming sound from the speaker. Around 3 seconds later transistor C1364 blew it's cover and I switched off immediately (see attached for pics). The OP's I used were BD124's with genuine driver Q's.

I've done a quick test and have a possible dead OP and a dead C1124 driver.

I am about to remove the OP's again, along with a few other components, but is there certain area's you guy's would recommend that I looked at? It's such a shame as it was running really well, besides a few crackles on the R channel
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Old 2nd Apr 2017, 8:30 pm   #53
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Default Re: It all ended with a bang...

Operating an amplifier with an intermittent connection to the speaker is quite an effective way of using the speaker inductance to generate back-EMF to zap transistors. Some amplifiers have no protection against this, some have a bit and a few have good effective protection.

The transients generated can be quite a bit faster than some protection arrangements can act.

So if you think a speaker connection is dodgy, it's best to investigate with an ohmmeter and power off on the amp.

Crackles can be from dry solder joints so it's worth re-flowing the joints for components which get hot or suffer vibration.

Pots are another common source.

Swapping the signals to the power amps over can isolate a fault to preamp or power amp stages. Seeing whether volume, balance and tone controls have any effect (like changing the sound of the crackles) can provide further clues, seeing whether the crackles are on tape outputs, is another check.

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Old 2nd Apr 2017, 9:18 pm   #54
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Default Re: It all ended with a bang...

Thanks David

Noob mistake. I will check and replace the bits I have blown into orbit and sort out the defective connection... Someone else said this would be a steep learning curve I am praying I haven't fried the unit!


Gareth
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Old 3rd Apr 2017, 9:11 am   #55
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Default Re: Sony HP-511 - Blowing Fuses

Threads merged. Some posts deleted.
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Old 3rd Apr 2017, 11:42 am   #56
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Default Re: Sony HP-511 - Blowing Fuses

Got it now! I answered the other thread. If you want another pair of eyes and hands, I'm in Whitchurch Village just south of the city. NB I'm not a transistor specialist but we could take a look at the kind of steps David has suggested.
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Old 9th Apr 2017, 11:43 am   #57
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Default Re: Sony HP-511 - Blowing Fuses

I've replaced the blown components, turned out to be 2 OP's not just the one.

I have checked the readings on a DMM and all seem good except for one OP. It reads 550 on one pinout and 990 on the other. I have swapped the Q out for another and have the same reading. I did notice this before I powered it on before so this hasn't been a case of the most recent power on - The OP in question is 0512 2SD291

Is this a problem? Could this be a short or another faulty component? Need I worry? The OP with the strange reading is not an OP that failed when it powered on.


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Old 14th Apr 2017, 2:56 pm   #58
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Default Re: Sony HP-511 - Blowing Fuses

I've fired up the unit on the LL again. It is the Left channel that has the issue, not the Right channel as I stated earlier.

There is a video of the problem here; https://youtu.be/vl7CUHWUjUE
It's recorded directly into the camera audio input and running out of the headphone jack on the Sony unit. The left channel begins to hum/distort but by switching the stereo/mono button off and on it clears for around a second before returning. It also seems to do this when turning out and back into a radio station.

Any thoughts guys?


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Old 15th Apr 2017, 5:44 am   #59
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Default Re: Sony HP-511 - Blowing Fuses

Agggh, going to clean my ears out with some 70's rock music! : ) Got a bit lost, re read the threads, but non the wiser. Can you clarify, is this hum on both or one channel? Sounds like 100hz power supply hum, have you powered it up off the LL?

I'd take Roger up on his kind offer and have a pootle over to his. This job really needs a scope and a bit more experience.

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Old 15th Apr 2017, 9:31 am   #60
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Default Re: Sony HP-511 - Blowing Fuses

Apologies haha. The hum is only on the Left channel, the right stays clear. Yes it's on the LL. Last time I had it at this state, I plugged it directly into the mains and blew a couple of OP's, a driver and blew the cover off another Q instantly. No more blown fuses though

I have spoken to Roger and upon his advice I have tested the unit from another input source. Running an auxiliary input gives the same results.

I think you're right, it's time to get someone else involved as I have absolutely no idea.

Thanks for your help and i'll hopefully be back with a working unit soon.


Gareth

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