[low_bass_makker]

Originally Posted by DerAlte

Capacitors do fail sometimes on their own (component failure), but that is extremely rare. The only thing that can make a cap fail usually is a massive spike, which usually ruptures or dislocates body of the cap. It is highly unlikely that a 102pF 50V ceramic fails in 12VDC equipment. If one applies upwards of 200V DC or AC on a 50V ceramic cap, one will find only the leads on the PCB and minute pieces scattered on the PCB, but no smoke.

Sirji the 12 vdc equipment is not working at that level there is a dc-dc converter which increases the voltage to make the 300 watts rms. Approx 34 volts

Originally Posted by ibm_jennifer

We have replaced the blown out capacitors, but the original problem (dup dup sound in front speakers) still exists. Once the amp is switched on, I can hear deep dup dup sound from the front speakers even if the volume level is zero.

I think if the pre amp is the culprit there must the grounding issue with the amp. It might have cause when the speaker wire touches the ground causing the ground to get damage. Which in case you IC in the pre amp.

Yes you can run the amp without the PRE-Amp section but all the filters and gains setting will be lost.

[flipsyde]

Hey, try MICHEAL - 9884548351. He works out of his shop in Adyar opposite Malar hospital. You'l have to take the lane which leads to Shankara School. Give him a call before you drop in. I was referred to him by a guy in Burma Bazzar who deals with car audio.

Yes there is a product called JBL 75.4 II but I don't think it ever retailed in India. If I;m not wrong that was only for the American and European market.

[panky12345]

Originally Posted by flipsyde

Yes there is a product called JBL 75.4 II but I don't think it ever retailed in India. If I;m not wrong that was only for the American and European market.

You're very much right, the products are identical in specs, appearance etc.. only difference is that the company adds II after the model # for North American market.

[DerAlte]

Originally Posted by low_bass_makker

Sirji the 12 vdc equipment is not working at that level there is a dc-dc converter which increases the voltage to make the 300 watts rms. Approx 34 volts ...

Woheech, sir! The 34V is for the output section to keep current low. But even then, at the locations the low-voltage caps are placed one doesn't expect spikes to exceed 2x the normal voltage. Destructive failure needs 4x at least (OK, there is a curve for it, and it is the pulse energy that counts).

[ibm_jennifer]

You're very much right, the products are identical in specs, appearance etc..

No, its not TRUE. There are many differences between them, here are some:

GTO 75.4 RESISTOR RES-00-00437 1/5WF 1K OHM R120,220,320,420
GTO 75.4II RESISTOR RES-00-00545 1/5WF 5.6K OHM R120,220,320,420
GTO 75.4 RESISTOR RES-00-00417 1/5WF 13.7K OHM R171,271,371,471
GTO 75.4II RESISTOR RES-00-00508 1/5WF 33K OHM R171,271,371,471
GTO 75.4 RESISTOR RES-08-00225 SMD 0805 1/8WJ 820
OHM
R108,208,308,408
GTO 75.4II RESISTOR RES-08-00242 SMD 0805 1/8WF 240
OHM
R108,208,308,408
GTO 75.4 RESISTOR RES-08-00022 SMD 0805 1/8WF 15K
OHM
R155,255,355,455
GTO 75.4II RESISTOR RES-08-00116 SMD 0805 1/8WF 9.1K
OHM
R155,255,355,455
GTO 75.4 RESISTOR RES-08-00239 SMD 0805 1/8WF
9.31KOHM
R257,457
GTO 75.4II RESISTOR RES-08-00200 SMD 0805 1/8WJ 5.1K
OHM
R257,457
GTO 75.4 CAPACITOR CEC-08-00009 SMD 0805 12PF C156,356
GTO 75.4II CAPACITOR CEC-08-00023 SMD 0805 22PF C156,356
GTO 75.4 CAPACITOR CEC-08-00017 SMD 0805 20PF C256,456
GTO 75.4II CAPACITOR CEC-08-00037 SMD 0805 39PF C256,456
GTO 75.4 POWER TERMINAL TER-00-00241 (3P) DST0013-00 TER01

GTO 75.4II POWER TERMINAL TER-00-00277 (3P) DK-03B03-AG-1-DN TER01
GTO 75.4 SPEAKER TERMINAL TER-00-00251 (8P) ST-11A-2-8P TER02

GTO 75.4II SPEAKER TERMINAL TER-00-00273 (8P) DK-0802-AG-1-DN TER02

[ibm_jennifer]

Guys,

The amp is ready and its working fine now. The total damage is Rs. 750. He has replaced the PreAmp board from a damaged unit(we have sourced it from a import party). Thanks guys, specially Sam for your help and support.

[panky12345]

Originally Posted by ibm_jennifer

No, its not TRUE...TER02

Sorry bhai, never went into these details.. care to explain what difference does these numbers make vis-a-vis the output?

[ibm_jennifer]

what difference does these numbers make vis-a-vis the output

Nothing noticeably. Sam may be aware of.

[ibm_jennifer]

I heard 75.4 works under 230mV to 6V where the impute sensitivity of 75.4 II is 73mV to 6V. Am i right Sam?

[ibm_jennifer]

No reply from Sam, So I am here to confirm that its True and my Amp is 75.4II which has sensitivity control from 73mV to 6V.

[Sam Kapasi]

Glad that everything is sorted out. Panky there are no noticeable differences between 75.4 and 75.4II, just some standard ongoing changes in batch numbers.

[panky12345]

Originally Posted by ibm_jennifer

my Amp is 75.4II which has sensitivity control from 73mV to 6V.

Even mine is 75.4 II cheers:

[Ajaybiz]

Folks need help for my 75.4 as its long pending task the front channels are keep on going kaput specially driving in sunny days, tried putting cooling fan but waste, last time my installer did some soldring in preamp unit as is was loose as per him, can changing the preamp solve this issue?need a proper repairing shop in Bangalore no installer or chotu please.

[nitrous]

Originally Posted by Ajaybiz

Folks need help for my 75.4 as its long pending task the front channels are keep on going kaput specially driving in sunny days, tried putting cooling fan but waste, last time my installer did some soldring in preamp unit as is was loose as per him, can changing the preamp solve this issue?need a proper repairing shop in Bangalore no installer or chotu please.

Contact Blueraven.
I had an issue with one of my 75.4s and he got it repaired for me.

[saurabhkum]

Need help in getting my JBL 75.4 checked , the sound sometimes goes away and Amp lims into protect mode then again come back after some times. What could be the problem ? Also if any decent place where can I get the same checked.