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Old 2nd March 2009, 02:04 PM   #1
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Join Date: Feb 2009
Question New member 800a2 ?

I have a 800a2 it quit working about five years ago i was going to sent out to have it fixed until i found thread on here which helped me trouble shot it. This is what i found so far three of the 0.1 resistor's are bad on the left side they read over 400K so i pulled all ten resistor's on the left side now the 800a2 powers up right side works great. Now here where i need some help this is what i have tested so far

R228 100 ohm
R229 100 ohm
R225 100 ohm
R226 100 ohm

R279 50 ohm
R278 50 ohm
R277 50 ohm
R276 50 ohm
R275 50 ohm
R252 50 ohm
R251 50 ohm
R250 3.87M ohm BAD
R249 50 ohm
R248 50 ohm

For the IRF640 and IRF9640 not even going to just replace them and the same for the A06 & A56.

Now is there anything else i should test or replace? I going to make my parts order tomorrow. Any help would be appreciate.
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Old 2nd March 2009, 02:13 PM   #2
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Join Date: Nov 2003
Location: Louisiana
R262, 263, 234, 235, 237, 238, 239, 241, 243, 245, 264, 265, 267, 269, 271, 273, and recheck the 51 ohm resistors after removing the outputs.
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Old 2nd March 2009, 09:15 PM   #3
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Join Date: Feb 2009
I checked the ones you listed and i recheck the 50 ohm. What do you think?

R262 47 ohm

263 20 ohm

234 20 ohm

235 20 ohm

237 101.1 ohm

238 47.1 ohm

239 100.2 ohm

241 232.7M ohm bad

243 100.4 ohm

245 100 ohm

264 39.1 ohm

265 100 ohm

267 100 ohm

269 100 ohm

271 100.7 ohm

273 100.4 ohm

R279 50.1 ohm
R278 51 ohm
R277 51.1 ohm
R276 51 ohm
R275 50.9 ohm
R252 51.2 ohm
R251 50.9 ohm
R250 3.87M ohm BAD
R249 50.9 ohm
R248 50.9 ohm
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Old 2nd March 2009, 09:29 PM   #4
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Join Date: Nov 2003
Location: Louisiana
R262 also appears to be defective.

You need to check Q229, 230, 224, 225.

With a lighted magnifying glass, examine (or test) the rest of the SMD resistors in this channel to see if any have visible signs of damage.
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Old 3rd March 2009, 02:46 AM   #5
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Join Date: Feb 2009
Quote:
Originally posted by Perry Babin
R262 also appears to be defective.

You need to check Q229, 230, 224, 225.

With a lighted magnifying glass, examine (or test) the rest of the SMD resistors in this channel to see if any have visible signs of damage.

I rechecked R262 it is 20 ohm my bad now for the Q229, 230, 224, 225. i going to replace with to be on the safe side . I checked all the other Resistor's and they are all good. Here my next Q what is the bast way to reattach the IRF 640 & 9640 the Mehsa board? This is how i removed the old ones i slowly headed the mehsa board up the until they came loose i was thinking of doing the same heat the board until the solder melted then put them back on then a quick cool down. what do you think?
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Old 3rd March 2009, 12:18 PM   #6
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Join Date: Nov 2003
Location: Louisiana
You first need to tin the back of the new transistors. The Fairchild transistors are easier than the IR transistors (which have a near mirror finish on them and sometimes resist taking solder). You need to do this at a low temperature. 600F seems to be safe. Even at low temps, you need to do it as quickly as possible.

http://www.bcae1.com/temp/ttrockford...transistor.jpg

After tinning them, check the resistance from the gate to either of the other legs. You should read infinite resistance (same as when the probes are not in contact with anything). If you read anything else, the transistor has failed.

Bend the leads and solder the center leg in place with the transistor laying as flat as possible on the insulator. It won't lay completely flat because if the solder on the back of the transistor. Heat the back of the insulator and apply pressure to the top of the transistor. When the solder gets hot enough, the transistor will drop onto the insulator. At that point, remove the heat and continue to hold pressure on the transistor until the solder freezes.

To prevent adjacent components from lifting when heating the insulator, use binder clips to hold them down.

http://www.bcae1.com/temp/ttpunchbinderclips.jpg
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Old 3rd March 2009, 09:33 PM   #7
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Join Date: Feb 2009
Quote:
Originally posted by Perry Babin
You need to check Q229, 230, 224, 225.
here on more for you should replace Q209 & Q210?

PS sorry about the type O's how do you edit your own post on here?
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Old 3rd March 2009, 09:42 PM   #8
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Join Date: Nov 2003
Location: Louisiana
I don't remember those failing but anything is possible.

You have a limited time to edit the posts. Using a browser with spell check helps catch some of the typos. If you catch them quickly, the edit button at the bottom of the post will bring up an editing window.
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Old 4th March 2009, 08:02 AM   #9
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Join Date: Feb 2009
Quote:
Originally posted by Perry Babin
I don't remember those failing but anything is possible.

You have a limited time to edit the posts. Using a browser with spell check helps catch some of the typos. If you catch them quickly, the edit button at the bottom of the post will bring up an editing window.

There no edit tab I guess since I am new I don't have that option yet. Now back to the amp when I get all the parts in and test it I will post a update on how it working. I appreciate the help. Thanks again.
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Old 5th March 2009, 01:55 AM   #10
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Join Date: Feb 2009
Perry i could not find the LVR-3 0.1ohm 3W resistor's every place i checked was out of stock so i ordered LOB-3 .1ohm 3W in it's place have you ever use these? let me know.
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