Help needed, Lanzar opti 2500

Leif · 18th January 2009, 07:34 AM

Hello everyone,
I have now an broken old Lanzar opti 2500 on my workbench and it seems like the preamp is broken. The amp section in it self works.
All inputs and gain&bassboost works, but when i increase volume distorssion accrue. In mono mode a very week and highly distorssion signal comes out from the amp.
I measured that the op-amps (U1-U4) gets a voltage of 28V.
So i wonder where the problem could be.

thanks!

-Leif-

Perry Babin · 18th January 2009, 07:48 AM

Does the rail voltage remain constant when you try to drive it to high power?

With no RCAs plugged in, do you read ~0 ohms between the RCA shield and the non-bridging speaker terminals?

Do you have an oscilloscope?

Leif · 18th January 2009, 08:20 AM

Hi,
The rail voltage is in idle about 92V and when i push it higher rail voltage variate between 70 - 110V.

With no RCA connected there is about ~0 ohms between rca gnd and non-bridging speaker terminals.

I have not got a oscilloscope at home right now, but tomorrow i can borrow one from work.

Perry Babin · 18th January 2009, 08:39 AM

Assuming that this is essentially the same as the 50c, Q1 and Q3 are the muting transistors. With the black meter probe on the RCA shield, what DC voltage do you read on the 3rd leg of Q1 and Q3?

Leif · 18th January 2009, 08:45 AM

Both Q1 and Q3 has -14.5VDC on leg 3

Perry Babin · 18th January 2009, 08:59 AM

That's OK.

Transistors Q4 and Q5 are the input to the power amplifier's differential amp. If the signal is clean there, the problem is in the power amplifier. If it's not clean there, the problem is before the power amp. Check the signal at the output pins of each of the op-amps to see where it becomes distorted.

Leif · 18th January 2009, 09:08 AM

ok, thanks for now.
I have to borrow a oscilloscope from work to check that, but it has to wait to tomorrow.

Leif · 18th January 2009, 10:10 AM

ok, a new problem after bending Q4... DC in speaker outputs...

Q4 and the other transistors do not have any short circuits, but in the speaker right channel output is -13VDC and in the left +13VDC.
Rail voltage is now about 107V

My DC power supply is set to 12.2VDC

So wtf just happend?

PQatPIT · 18th January 2009, 11:30 AM

Ha! Another Finland guy with broken Opti2500.

I have a similar one, with power supply down. Some resistors burned black and just wanted to know their values, otherwise it seems to be ok. Those resistors route power supply fets their pwm signal. Bought it like that as a project, just haven't had time to repair.

When I was young I drooled for one and I just couldn't keep my hands of of it

. Maybe we should join forces here? Email pq (at) pitsop.fi.

Leif · 18th January 2009, 12:17 PM

Alright,
I´d just e-mail you PQ, but your e-mail address seems to bee wrong... even with the @

I wonder how many of those amps is sold here in finland? They were quite expensive...

What components are you interested to know?

18th January 2009, 07:34 AM	#1
Leif diyAudio Member Join Date: Nov 2004 Location: Finland	Help needed, Lanzar opti 2500 Hello everyone, I have now an broken old Lanzar opti 2500 on my workbench and it seems like the preamp is broken. The amp section in it self works. All inputs and gain&bassboost works, but when i increase volume distorssion accrue. In mono mode a very week and highly distorssion signal comes out from the amp. I measured that the op-amps (U1-U4) gets a voltage of 28V. So i wonder where the problem could be. thanks! -Leif-

18th January 2009, 07:48 AM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Does the rail voltage remain constant when you try to drive it to high power? With no RCAs plugged in, do you read ~0 ohms between the RCA shield and the non-bridging speaker terminals? Do you have an oscilloscope? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

18th January 2009, 08:39 AM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Assuming that this is essentially the same as the 50c, Q1 and Q3 are the muting transistors. With the black meter probe on the RCA shield, what DC voltage do you read on the 3rd leg of Q1 and Q3? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

18th January 2009, 08:59 AM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	That's OK. Transistors Q4 and Q5 are the input to the power amplifier's differential amp. If the signal is clean there, the problem is in the power amplifier. If it's not clean there, the problem is before the power amp. Check the signal at the output pins of each of the op-amps to see where it becomes distorted. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

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18th January 2009, 08:20 AM	#3
Leif diyAudio Member Join Date: Nov 2004 Location: Finland	Hi, The rail voltage is in idle about 92V and when i push it higher rail voltage variate between 70 - 110V. With no RCA connected there is about ~0 ohms between rca gnd and non-bridging speaker terminals. I have not got a oscilloscope at home right now, but tomorrow i can borrow one from work.

18th January 2009, 08:45 AM	#5
Leif diyAudio Member Join Date: Nov 2004 Location: Finland	Both Q1 and Q3 has -14.5VDC on leg 3

18th January 2009, 09:08 AM	#7
Leif diyAudio Member Join Date: Nov 2004 Location: Finland	ok, thanks for now. I have to borrow a oscilloscope from work to check that, but it has to wait to tomorrow.

18th January 2009, 10:10 AM	#8
Leif diyAudio Member Join Date: Nov 2004 Location: Finland	ok, a new problem after bending Q4... DC in speaker outputs... Q4 and the other transistors do not have any short circuits, but in the speaker right channel output is -13VDC and in the left +13VDC. Rail voltage is now about 107V My DC power supply is set to 12.2VDC So wtf just happend?

18th January 2009, 11:30 AM	#9
PQatPIT diyAudio Member Join Date: Nov 2008	Ha! Another Finland guy with broken Opti2500. I have a similar one, with power supply down. Some resistors burned black and just wanted to know their values, otherwise it seems to be ok. Those resistors route power supply fets their pwm signal. Bought it like that as a project, just haven't had time to repair. When I was young I drooled for one and I just couldn't keep my hands of of it . Maybe we should join forces here? Email pq (at) pitsop.fi.

18th January 2009, 12:17 PM	#10
Leif diyAudio Member Join Date: Nov 2004 Location: Finland	Alright, I´d just e-mail you PQ, but your e-mail address seems to bee wrong... even with the @ I wonder how many of those amps is sold here in finland? They were quite expensive... What components are you interested to know?

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