BigB 24 Posted April 18 Share Posted April 18 Hello all. I recently acquired some carver gear. An M500t amp and a TFM 35 amp. Looking for some direction on the M500. I understand it’s a dual voltage unit using low and high voltages on the rails. My issue is the relay doesn’t close upon power up. I’m leaning toward the op amp or something in that circuit. All the rectifiers check out good but I’m only getting around 30v on the low V side. Not the 40v it’s showing in the manual. The relay is good as I have supplied 24v to the coil to test it. I know these amps are different than most I’ve worked on but I’m ready to tackle this one. Thanks in advance for any input and I look forward to interacting with all of you. Cheers. 12 Link to comment Share on other sites More sharing options...
Dennis47 888 Posted April 18 Share Posted April 18 WELCOME @BigB! Link to comment Share on other sites More sharing options...
Zenith4me 1,422 Posted April 18 Share Posted April 18 Welcome to TCS! Link to comment Share on other sites More sharing options...
Cring08 177 Posted April 18 Share Posted April 18 WELCOME! Link to comment Share on other sites More sharing options...
wrf 4,245 Posted April 18 Share Posted April 18 if the relays are not engaging, your amp is likely in protection. Something has gone wrong. Suggest you start with downloading the service manual. Check the output transistors for shorts. Also check for DC offset at the outputs (up stream from the relays). This may help narrow down why its going into protection. 3 Link to comment Share on other sites More sharing options...
Community Admin AndrewJohn 8,735 Posted April 18 Community Admin Share Posted April 18 Welcome @BigB, glad you found us! Keep us posted as you put your 500 back in service. 2 Link to comment Share on other sites More sharing options...
BigB 24 Posted April 23 Author Share Posted April 23 Checked MV at TP 3,4. Have 5.1v. VR 102 had no effect. Should be around 6mv. Looks like an issue to me 3 1 Link to comment Share on other sites More sharing options...
BigB 24 Posted April 23 Author Share Posted April 23 I checked all of the output transistors Q119-126 as well as Q118,119,109,110,116,117. All test good 2 Link to comment Share on other sites More sharing options...
timmyjim 356 Posted April 23 Share Posted April 23 5 hours ago, BigB said: Have 5.1v. If you have 5.1V between TP3 and TP4 ....... your amp is on fire. 2 Link to comment Share on other sites More sharing options...
BigB 24 Posted April 24 Author Share Posted April 24 TP3 or TP4 to ground is 5.1vdc. TP1,2 to ground is 100mvdc. I checked all of the outputs and they test fine. I’m thinking another transistor on the board ? 2 Link to comment Share on other sites More sharing options...
Daddyjt 8,747 Posted April 25 Share Posted April 25 You need to test TP 1 to TP 2 - NOT to ground… same with 3 & 4. 4 1 Link to comment Share on other sites More sharing options...
BigB 24 Posted May 2 Author Share Posted May 2 Gonna do some more testing on this M500t. I found several bad resistors and replaced them it there must be a reason they failed. Looking at transistors now and found Q116,118 shorted. My main voltages look good (42 and 74v ) from the power supply. This is a way different amp than I’m used to. 2 Link to comment Share on other sites More sharing options...
Kurt 2,055 Posted May 3 Share Posted May 3 Welcome to the Carver Site! Link to comment Share on other sites More sharing options...
Receiver2000 2,879 Posted May 3 Share Posted May 3 WELCOME!!!! Link to comment Share on other sites More sharing options...
BigB 24 Posted May 27 Author Share Posted May 27 Update on the M500t. Replaced several transistors in this unit and recapped it. Also changed out some toasted resistors. DBT indicates no shorts but still no speaker relay. I’m also getting some odd voltages from the transformer. Can you test these V from chassis ground or transformer center tap(black wire) ? The circuit to D601 is only reading around 5.7v a/c. D601 is outputting 21.5vdc. That is checking + to - with a meter on dc. Link to comment Share on other sites More sharing options...
BigB 24 Posted May 27 Author Share Posted May 27 I forgot to add that the transformer is humming also. Link to comment Share on other sites More sharing options...
Receiver2000 2,879 Posted May 27 Share Posted May 27 Dang, sure hope you get it sorted soon and start rockin!!!⁸ Link to comment Share on other sites More sharing options...
Rob 4,545 Posted June 15 Share Posted June 15 Welcome to the club!!! Link to comment Share on other sites More sharing options...
BigB 24 Posted September 5 Author Share Posted September 5 Hello all. It’s been a minute since I’ve worked on my M500t amp. I was having issues with the relay not closing and I have since replaced pretty much every transistor and some questionable resistors. This is unlike any amp I’ve worked on before. I seem to have proper V where it should be but obviously not where it needs to be. Is the triac problematic in these amps? I accidentally shorted mine and it took out a few components but I replaced them and it seems to be back on track. Could one of the IC chips be an issue? Any more help would be appreciated. This dual voltage stuff and how it works is a little confusing. Thanks in advance Link to comment Share on other sites More sharing options...
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