Marantz SR18 I would like to know if you can sell me 4 resistors .1ohmx2 5watts(bias resistor) it seem that it's verry hard to get Thank's

I would also replace 2sa992 (2pcs) and 2sc1845 on preamp board- sometimes they look ok when you test them by regular meter. Check 1.2 kOm and 4.7ohm resistors at preamp pcb. Check diodes on output pcb (could be smd type, connected from base of output transistors to emitter i think)

Solved the problem by analysing the circuit and fitting the appropiate resistor.

Thank you

Not knowing what kind of equipment you have, its hard to say, but .10 watt? Sounds like the buffer or driver also got involved. Usually you get 1/4-1/2 watt to the driver on a stock radio. I would also check the bias resistors like you suggested. Also check for burnt foil around the final you replaced. Good just be a slightly damaged circuit. Let me know if this helps.
Tom

Hi

Have you checked and set the bias current for the output stage. These 2 resistors will get hot if the bias is too high. Is it the firsy time you have fired the amp up? Operating in this condition may cause the output transistors to fail. If the output transistors are damaged,you would also experince heating of these resistors. Get back to me please and let me know if you have set bias

regards
robotek

Hello renning,

You may not have to buy a new board. It just might be the Convergence Amplifiers that have gone bad. You may just want to replace them first and then see if it corrects your problem before getting the whole board. The convergence amplifiers are easily identified they are tow big black modules attached to a big metal frame called a heat sync, normally it will be located on the right rear section of the TV set looking at it from the back or it would be located in the middle rear of the set looking at it from the rear. In any even look for two big six sided black components with 21-22 pins, now this is the important parts some electronics parts stores sell what are called Convergence Kits (Yes this problem is so common that they have put kits together to repair this issue), they contain the two modules and the biasing resistors needed to properly do the job. You will have to order the kit for your make and model of TV if they do not have a kit, you will have to use a schematic diagram to find the values of the biasing resistors needed. Once you have the modules and the biasing resistors, you will have to de-solder the modules and the associated resistors and replace them with the ones you purchased. You will also need to detach the modules from the heat sink clean the heat sink (with alcohol) and then attach the new modules (with a new application of heat sink paste, which is the white stuff the you removed with the alcohol) with the screws you removed to detach the modules. Once the modules and biasing resistors are installed you will need to turn on the TV and then perform a convergence setup, your TV most likely will have an auto convergence alignment setup feature on the setup menu , use this to do the convergence alignment setup (check your users manual for help in doing this). The cost for this repair will be as follows:

2 STK392-1XX series Convergence Amplifiers $4.00-$15.00 USD Total $8.00 - $30.00 USD

9-10 biasing resistors $5.00-$10.00 USD (multipack) $15.00 USD

Solder $5.00 USD

Soldering Iron $20.00 USD

Silicone Heat sink paste $6.00 USD

de-soldering brade $5.00

The cost of materials will be about $81.00 on the high end.

The cost of a new board will be about $150.00 - $200.00 depending on the vendor.

You can buy replacement boards from a manufacture approved vendor outlet, go to the manufacture's site find support and parts they should have a listing of supported vendors. I would suggest calling the vendor and ordering from the phone asking them to send you an RMA for the part (board) this protect you from having them asses charges without delivery of product.

You will need the schematic diagram to help you install it schematics can be purchased at http://www.servicemanuals.net
for about $19.00 USD.

I hope this helps,

Thank you,

Shuttle83

Hello n0lcl285,

I gave this advice before and I hope it helps you too.

You may not have to buy a new board. It just might be the Convergence Amplifiers that have gone bad. You may just want to replace them first and then see if it corrects your problem before getting the whole board. The convergence amplifiers are easily identified they are tow big black modules attached to a big metal frame called a heat sync, normally it will be located on the right rear section of the TV set looking at it from the back or it would be located in the middle rear of the set looking at it from the rear. In any even look for two big six sided black components with 21-22 pins, now this is the important parts some electronics parts stores sell what are called Convergence Kits (Yes this problem is so common that they have put kits together to repair this issue), they contain the two modules and the biasing resistors needed to properly do the job. You will have to order the kit for your make and model of TV if they do not have a kit, you will have to use a schematic diagram to find the values of the biasing resistors needed. Once you have the modules and the biasing resistors, you will have to de-solder the modules and the associated resistors and replace them with the ones you purchased. You will also need to detach the modules from the heat sink clean the heat sink (with alcohol) and then attach the new modules (with a new application of heat sink paste, which is the white stuff the you removed with the alcohol) with the screws you removed to detach the modules. Once the modules and biasing resistors are installed you will need to turn on the TV and then perform a convergence setup, your TV most likely will have an auto convergence alignment setup feature on the setup menu , use this to do the convergence alignment setup (check your users manual for help in doing this). The cost for this repair will be as follows:

2 STK392-1XX series Convergence Amplifiers $4.00-$15.00 USD Total $8.00 - $30.00 USD

9-10 biasing resistors $5.00-$10.00 USD (multipack) $15.00 USD

Solder $5.00 USD

Soldering Iron $20.00 USD

Silicone Heat sink paste $6.00 USD

de-soldering brade $5.00

The cost of materials will be about $81.00 on the high end.

The cost of a new board will be about $150.00 - $200.00 depending on the vendor.

You can buy replacement boards from a manufacture approved vendor outlet, go to the manufacture's site find support and parts they should have a listing of supported vendors. I would suggest calling the vendor and ordering from the phone asking them to send you an RMA for the part (board) this protect you from having them asses charges without delivery of product.

You will need the schematic diagram to help you install it schematics can be purchased at http://www.servicemanuals.net
for about $19.00 USD.

I hope this helps,

Thank you,

Shuttle83

OOPS-forgot to mention if your bias turns out ok after replacing any blown outputs, turn it off and resolder the collectors (center) pins of all 4 output transistors and turn it back on-should work but you'll need to recheck bias and dc offset. They appear to both be adjustable on the board sticking up on the top side-it's right in the middle and has 4 trim pots on it......

Your no doubt finding the speaker safety/turn on surge protect relay NOT engaging a few seconds after turning it on-right? Check the output transistors. These are the big green and black ones screwed to the heatsink. You gain access to them by taking off the bottom cover. There's 4 per channel--2 green and 2 black. You'll probably find one or more of them shorted. If you find replacements, put them in exactly as the originals with new thermal grease/heatsink compound. Unsolder and lift the center pin (collector) on each of the four transistors of the effected channel. Power it up and check across the outside pins of each device for proper bias-about a half a volt or so on each one. If the voltage is much higher, or not there you've got other problems that will require more diagnostic/troubleshooting. Do all the lights on the front panel work-or just the tape monitor indicators? If just the tape monitors light up, check resistors RN83 and RN84 on main board under the speaker connector board-remove the speaker connector board to get at them. These are bad on mine and I've yet to replace them. I believe these to be 920 ohm 1% precision resistors....

www.futurlec.com
0.20 US each

This denotes that the convergence amps are going bad or the biasing resistors are failing. Check the bias voltages on the amplifiers to determine if this is indeed the problem. If it is try to replace the biasing resistors first, then if this does not clear up the problem, replace the convergence amplifiers. Also check the convergence coils for problems.

I hope this helps,
Thank you,
Shuttle83