Info on this pair of A1943/C5200

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#42
Toshiba 1943/5200 are 250/pair last time I purchased from Railton. That was sometime last year.

Miracle 300VA is different core - 128mm diameter. The 225VA corresponds to your transformer of 112x57. 160VA is 107x52. All uncomfortably close together, and no idea of winding wire so no clue as to what the transformer actually is just by looking at it.
 
#43
sangram said:
Toshiba 1943/5200 are 250/pair last time I purchased from Railton. That was sometime last year.

Miracle 300VA is different core - 128mm diameter. The 225VA corresponds to your transformer of 112x57. 160VA is 107x52. All uncomfortably close together, and no idea of winding wire so no clue as to what the transformer actually is just by looking at it.
Click to expand...


Well here is the bomb.

While the discussion was going on here, I was also mailing Mr. Shyam Bajaj wanting to know the VA of the toroid. He is right now abroad and cannot spare time.

I asked him like this:
-------------------------------
Dear Sir,

***********

Can you kindly tell me which speakers will be the best match for Norge 1000. Norge Millennium Speakers or Norge TWR 125 Mk III.

Lastly, for my own personal interest I am waiting for you to the tell me the VA rating of the transformer. My guess is 225 ~ 300 VA. Also what it the current rating of the two secondaries:
+/-30 V X ?A
+/-15V X ?A

Thanks in advance.

Warm Regards,
*************
----------------------------------------------------

He replied:

+/-30 V X ?A...500 VA.
+/-15V X ?A ...250VA approx.

------------------------------------------------


This means:
+/-30 V X 8.33A --> 500 VA.
+/-15V X 8.33A --> 250VA.

750VA toroid. This means the toroid in Norge 1000 weighs nearly 6.8 kilos. Considering that the amp weighs 8.75 kgs, the rest 2 kilos consists of the cabinet, heat sink & circuits.

I cannot believe. 😱
 
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#46
Average weight for 500VA 30V torroid is 3.5kg
A standalone 225VA 15V torroid is about 1.9kg

Concidering that we don't need two primaries, it would seem there is some room in that weight to exceed the 500VA rateing.

I still stand by the heatsinks being way to small.

Also concider that the transistors may survive a 250W pulse but what about a sustained chain of them?

Also a 250W transistor is not a 250 transistor if mounted in free air (or on tiny heatsinks).
 
#50
30VAC will get you 42VDC supply rails. That is unsafe with just one pair of outputs into 4 ohms especially with the small heatsinks. Judging by the 150-200VA transformer estimate, and the 2x4700uF per rail in the supply, the designer has used the principle of "power supply sag" to protect the transistors. However as they are poor quality counterfeit transistors, they aren't even handling that.
 
#51
Buy a digital multimeter.
Ensure it has DC and AC voltage reading scales.
It should have DC scales of 199.9mVdc, 1.999Vdc, 19.99Vdc, 199.9Vdc and 500Vdc
Preferably having the same five scales for AC measurement.
These ten scales are available on cheap meters. You do not have to spend anymore than $10 to $15.
Save the big spending until you become a serious DIYer.
Auto-ranging is not important. Resistance is useful.
Capacitance and hFE and frequency measurement are not needed

There is no point in following the DIYaudio hobby without tools.
 
#52
AndrewT said:
Buy a digital multimeter.
Ensure it has DC and AC voltage reading scales.
It should have DC scales of 199.9mVdc, 1.999Vdc, 19.99Vdc, 199.9Vdc and 500Vdc
Preferably having the same five scales for AC measurement.
These ten scales are available on cheap meters. You do not have to spend anymore than $10 to $15.
Save the big spending until you become a serious DIYer.
Auto-ranging is not important. Resistance is useful.
Capacitance and hFE and frequency measurement are not needed

There is no point in following the DIYaudio hobby without tools.
Click to expand...

Thanks for all the help & info guys. All the members of diyaudio are so knowledgeable, and the best part is, you guys treat noobs like us very kindly.🙂

Me and my friend will be going to the shop in Chandni Chowk as told by sangram in order to buy the transistors, and also the multimeter.
 
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#53
Update: Mr. Bajaj contacted me via mail. He said that the 750VA tranformer quote was wrong.

Being above eighty years old is taking its toll, and also he is currently abroad, he will be back in India next week and reconfirm the toroid specs.

He also said the A1943/C5200 transistors are sourced from Taiwan, and are of very good quality and the same spec amps like Norge 1000 GOLD are exported to Great Britain, Norway, New Zealand, etc.

I will update here when i get his confirmation.

Thanks all you guys!!!
 
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#54
..... so many forum members consumed time to terminology and the rated power or real power of the amplifier... but also missed the obvious...

you need to actually hand make a schematic of the output so we can find out if this is a copy of the P3A from ESP or some other copy is EFP circuit ...

That can be simply seen by looking if the power suply is connected to the colectors or the emmiters of the output tranistors ....

in case that this is a copy of P3A and its CFP configured ( supply is to the emmiters )...then if bias is low .... then you might get away with it ...

If though its EFP configured ( supply is in the collectors ) then even if bias is low since there is no active VBE multiplier ( attached on heatsink) the amp will probaly suffer from thermal runaway .....


obviously when amplifier gets warm by playing bias will increase until shelf distruction ...

its not the first or the last time that someone copy a schematic that doesnt say that the VBE has to be attached to the main heat sink ....

regards sakis
 
#55
by the looks of the picture ...it seems to me that this is an EFP amplifier and simply they missed to attach the VBE multiplier on the heatsink ...

that is thermal runaway with a huge guarantee on it ..... will survive for casual listening of a few 10-15 watts but if pushed to anything like 40-50 watts for more than 30 minutes it will burn and shelf destroy with pleasure !!!

explosive regards
sakis
 
#56
Sadly we are dealing with someone who still has to buy a multimeter, solutions have to be tailored to a level the person attempting this doesn't feel in over his ears.

The rest of us fully understand what you are saying though.
 
#57
Hi guys, here is the update. My friend went to the shop as told by sangram a bought the pair of transistors. Also the multimeter.

We will be starting to do our DIY on the amplifier by tommorow.

Also, Sham Bajaj have informed us about the toroid transformer specs.The transformer is a 5 amp for 30-0-30, and 350 Ma for 15-0-15 winding.

60 X 5 = 300.00 VA [goes to Power amps]
30 X 0.35 = 10.50 VA [goes to Pre amps]
---------------------------
Total = 310.50 VA

Any idea about its true continuous power output per channel for this amp?


Transformer pics:

An externally hosted image should be here but it was not working when we last tested it.

http://www.freeimagehosting.net/2e8f6

An externally hosted image should be here but it was not working when we last tested it.

http://www.freeimagehosting.net/6a9f6

An externally hosted image should be here but it was not working when we last tested it.

http://www.freeimagehosting.net/93324

Diodes at +/-30V rails:
An externally hosted image should be here but it was not working when we last tested it.

http://www.freeimagehosting.net/0e778

Internal layout:

An externally hosted image should be here but it was not working when we last tested it.

http://www.freeimagehosting.net/7c158

An externally hosted image should be here but it was not working when we last tested it.

http://www.freeimagehosting.net/7b4db

Heatsink:
An externally hosted image should be here but it was not working when we last tested it.

http://www.freeimagehosting.net/29d90
 
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#58
Good going - did you get one pair or two pairs as advised? It's better to change out both pairs together and readjust the offset.

The transformer specs we'll have to go by what the manufacturer says as there is no way to measure it.

The heatsink I now recognise, it is one that I have also used. In the exact same configuration except mine are 4" high - the Norge ones look far shorter in length, probably a little under the 3.5" range? 3.2 - 3.3"? I use 2 of these 4" lengths for a 2x100W, 4 ohm amplifier built with LM3886 in parallel. I also use one 5.5" high unit of the same sinks for a 2x200W LM4780 BPA amplifier and both the sinks run quite warm even at moderate outputs, the BPA running quite warm at all times. I wouldn't trust it to hit 200W per channel, but then again I never plan to play it that loud 🙂

You can see some pictures here (not of completed amp, only chassis).

http://www.diyaudio.com/forums/parts/28068-india-chassis-knobs-pcb-makers-56.html#post2370190

So one 3.5" sink can do duty for about 70-80W amplifier. This translates to roughly 2x30-40W usable long-term power output for a stereo amplifier, not far from the estimates of many on this thread. This is quite apart from the fact that the Vbe multiplier is indeed missing, so the amp exploding doesn't come as a surprise.
 
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#59
sangram said:
Good going - did you get one pair or two pairs as advised? It's better to change out both pairs together and readjust the offset.

The transformer specs we'll have to go by what the manufacturer says as there is no way to measure it.

The heatsink I now recognise, it is one that I have also used. In the exact same configuration except mine are 4" high - the Norge ones look far shorter in length, probably a little under the 3.5" range? 3.2 - 3.3"? I use 2 of these 4" lengths for a 2x100W, 4 ohm amplifier built with LM3886 in parallel. I also use one 5.5" high unit of the same sinks for a 2x200W LM4780 BPA amplifier and both the sinks run quite warm even at moderate outputs, the BPA running quite warm at all times. I wouldn't trust it to hit 200W per channel, but then again I never plan to play it that loud 🙂

You can see some pictures here (not of completed amp, only chassis).

http://www.diyaudio.com/forums/parts/28068-india-chassis-knobs-pcb-makers-56.html#post2370190

So one 3.5" sink can do duty for about 70-80W amplifier. This translates to roughly 2x30-40W usable long-term power output for a stereo amplifier, not far from the estimates of many on this thread. This is quite apart from the fact that the Vbe multiplier is indeed missing, so the amp exploding doesn't come as a surprise.
Click to expand...

Got only one pair of transistors. Will buy another pair by tomorrow.

The heat sinks are 3.5 inches in height.

Just a 70 watt amplifier.😕

I wonder why do Norge quote 125 Watts X 2 @ 4 ohms?
 
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