search schematic Blaupunkt GTA 400

[Ground Zero]

Hello

I have bought an old amplifier Blaupunkt GTA 400 for 20 euros

i change 4 mosfet to the SMPS supply because 1 was burnt....

the sound of this amp is verry bad, so i keep only the smps to build my own amplifier

but i need to change other components because i can here a zzzz when the amp is power on without music
I think the noise is due to the rust on the resistance
the resistor is a 22 ohms and it comes verry hot when the supply works i don't know why ? can someone can explain me that please ?

I surrounded the rust on the resistor




This is the power supply with other condensators
i use 2 condensators of 10000µF low ESR for the secondary
2 condensators of 2200µF for the primary and 1 condensator of 1000µF near the terminals to replace the old condensator




I search the schematic of this amp, if someone have it can you give me please ?

Thanks in advance
hervé

[Ground Zero]

it seems my photos don't appears on the forum

i post another

the rust on the resistor and i mesure the temperature and i have musered 75°C on it but the supply works is it normal



the smps supply



Thanks for your help

[Perry Babin]

Can you post a photo of the bottom of the board?

Photograph it at a slight angle so that there isn't any glare from the flash.

[gisewhcs]

Hallo European neighbour!
I have schematics for serveral GTA amps, but not exactly for this one.
If you could post a pic from the solderside, it would really help, perhaps one of mine will be (nearly) the same!

[Ground Zero]

hello

Thanks for your answer

this is a photo



a photo where are solder the resistor who are verry hot 75 °C

The C is condensators with a value of 0.1µF "i think " on the condensator i can see 0.1 J 63 so i think 0.1µF 63 V ?



and i would like to know how can i do to have a +/-12 volts to power a preamp please?

[Perry Babin]

The snubber resistors will run hot but they may be running hotter than normal due to the two missing caps. From what I can see in the photos, there is one 2200uf on each side of the inductor. That leaves only one on the transformer's primary. That could cause more ringing on the primary which could cause the snubber resistors to run hotter.

The simplest option for the regulated preamp supply would be to use 7812 and 7912 regulators (if you want 12v instead of 15v).

The caps are 0.1uF@63 ±5%. Have you confirmed that they're not shorted?

[Ground Zero]

Thanks Perry

i will put the 2 missing condensators, but they are hot before i remove the 2 condensators so is it normal that resistors are hot ? and why?

Can you explain me what is the function of theses resistors please ?

for the capacitor i think there are ok i change them but i haven't tools to test them....

the preamp is this product

the aop are NE-5532 but i can change them and i put OPA2134PA from burr brown

Préamplification - Module Préamplificateur Buffer Stéréo AOP NE-5532

it works with a +/-15 V but i don't know the consump in A

Thanks for your help

[Perry Babin]

The missing caps were getting hot?

The snubbers (RC network) are used to damp ringing on the transformer. Under normal operating conditions, they will operate at slightly elevated temperatures. 75C is hotter than normal but, in some amps, they run that hot.

The 5532 is a perfectly good op-amp. There's no reason to change it. Current consumption of most op-amps used for preamp audio have negligible current draw unless you have a large number of them.

[Ground Zero]

the missing caps are not hot but they are old i'll change them with the same 2200µF because they are in // on the circuit

I change the NE 5532 because the sound was not clear with it but now with the burr brown it's better


This supply power up 4 channel amplifier

do you think i can use it with 2 module like that ?

PSC-Audio | Module PsC-Audio | FET100 - 100W @ 4Ohm; 65W @ 8Ohm ± 45V; 0,1%THD

the maximum current consump is 3 A by amp

the manual in *.pdf

http://www.psc-audio.ro/catalog/html...T100_print.pdf

Thanks

[Perry Babin]

If the audio wasn't clean from the 5532, it was defective or there was a problem with its power supply or the circuit it was in. No one can hear the distortion produced by a 5532 in a properly designed circuit. For those who want to argue this point, you'll have to go elsewhere. I won't be dragged into a senseless discussion. Douglas Self published distortion curves showing that it produced less than 0.001% THD + noise, even when loaded to 500 ohms (tough load for an op-amp).

What is the rail voltage produced by this power supply?

If it's more than 35v, you'll have to do something to drop the voltage before it's fed into the 7815/7915 regulators.

I wouldn't use this supply for much more than ~200 watts if you're going to drive the amps hard for long periods of time.