YBA DT INTEGRE - problem bias

Hi. Sorry for my english.
I have Yba Integre. When i rotate trimmer potentiomer for left channel to set bias, values for other channel also change? If i set 2-3mv for left channel, other channel automatic is 130mv. If i set 40mv for left channel, other channel is 105mv. When i set two trimmer potentiomet to min , on both channel i have 60mv.
Can you tell me how the transistors are located (TIP35/TIPC)
With RED dots, which are transistors? Tip 35 or tip 36?
 
There are at least 4 versions I think, a quick search spotted an alpha and a delta version, so its probably a shared supply in most of those, perhaps dud supply, loose shared grounding point, dead caps, something to track down starting with multimeter on the DC rails checking voltage stability and ripple, checking emitter resistors if appropriate. But always remove speakers and check DC offset on the output before anything else, fried speakers spoil your week!


[ edit I should have looked more carefully, DT seems to mean dual transformer, so probably separate supplies, but perhaps there's shared protection circuitry, thermistor, dodgy mains connection etc that's common to the channels. Or it might just be very flaky on both channels so they appear to interfere when are actually both wandering around? ]
 
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Now i set 2.5mv on left and right channel. On output terminal i have 70mv, after 2 minuts they are /left channel is (minus)-3mv, right channel is +5mv/. On collector TIP 35C/ TIP36C I HAVE +/-35V. Is it normal?
Do you know how many milivolts i need to set YBA Integre DT ALpha. This amplifier is with two transformers, and 6 big capacitors.
 
YBA Integre a single transformer

My YBA Integre a developed a distortion, and from what I was able to find on the web, it looks like the bias has drifted out of proper adjustment.
Does anyone know how to set the bias on this amp? I can not find any information about this anywhere.

A- where do on the board you read the mv?
B- what should the voltage be for proper operation?

Thank you
Petr
 
Here is the answer to which output transistor goes where and how to adjust the biases.

In the DT version, the transformers are not one for each channel.
Their secondaries are paralleled and wired as one transformer for each polarity.
This way the output stage has access to more current.

The biases going down with time is a known issue.
You can recognize the issue as soon as you hear a slight fuzz in the sound.
When the bias goes too low, you enter the crossover distortion zone.
The last time I had to deal with this issue, I replaced the original Piher PT-10 bias trimmers by PTC10LV10-103A1010, which should prove more stable with time.

I am at your disposal if you have more questions.

Michel
 

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Here is the answer to which output transistor goes where and how to adjust the biases.

In the DT version, the transformers are not one for each channel.
Their secondaries are paralleled and wired as one transformer for each polarity.
This way the output stage has access to more current.

The biases going down with time is a known issue.
You can recognize the issue as soon as you hear a slight fuzz in the sound.
When the bias goes too low, you enter the crossover distortion zone.
The last time I had to deal with this issue, I replaced the original Piher PT-10 bias trimmers by PTC10LV10-103A1010, which should prove more stable with time.

I am at your disposal if you have more questions.

Michel
Michel,
Thank you, very helpful.
Petr
 
hello michel,
i got a YBA integre from a friend , the right channel is dead. both tip35 are shorting out, also the drivers each243 and 253. one resistor probably 100 ohm (is that correct) and one with 10 ohm have blown.
a schematic would be very helpful for further troubleshooting, do you have one?
you write the transistors must be matched.
you have some in stock? i am interested in how ,much does it cost?

Priax
 

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Hello Priax,

You've got an early Integre here.
Its been a long while since I've seen overlapping mica insulators under the output transistors.
You have to cut them right in the middle between the transistors or replace them with smaller ones so they don't overlap.

You should replace all the 470 µF / 40 V capacitors with 63 V.
I have seen many fail over time.

I don't have a schematic but since one channel is OK you should be able to find the values easily there.
The TIP35C and TIP36C are discontinued in their original case (TO-218) and it is a problem for the Integre. They are mounted in close pairs and the new TIP in the TO-247 case are wider and will not fit. You sure will need to find originals and shop with great care as there is a lot of crap counterfeit TIP out there. Many counterfeited ST are available from China and they are very far from being as good as the originals. There is a very enlightening story on the subject on the researchgate . net site. I do have some in stock but they have been used before. As soon as I had to repair an Integre with failed outputs, I would replace the pair and keep the good one. I sure would be able to match a pair if you need. I may also have all the other parts you need, would have to check.

Make sure to verify the bias transistor, the one glued with epoxy as they often fail.
To contact me directly, go on the shipto . ca site, hover over Our services and choose Service center.

Best regards,

Michel
 
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hi michael i am from india . i have 3 yba alpha 1 power amps and looking to find out the output transistors. as no number written on the outputs

can u help me out with their original nos as i wanna buy them and keep it safe for future proof purpose as spares is very difficult to find in india

best regards
mallikh