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JoelG

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About JoelG

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    South Melbourne
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    Australia
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    Joel

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  1. Just thought I'd let you know how it went. Couldn't track down a service manual, not many of these made. But I took a reading off the "good amp" and adjusted the bias/idle to match then readjusted the DC offset and double checked the power consumption was equal. Both running at the same temperature now and sound much more present and responsive. Thanks again 👍
  2. Great, thanks! I'll I'll try to find out the specs and then give it a go. Much appreciate the info guys!
  3. Yes, sorry I couldn't work out how to send a clear copy. Yes, I can only see a pot for DC adjustment inside as well. I guess being a class A bias isn't usually s problem or something that needs adjusting?
  4. Hi, it's a ma7a, Japanese, runs on 105 volts.. it's basically the same as the European ma24a. I'll attach a schematic. Not sure how to check the bias? It's been running ok, without getting too hot but I'll try to pinpoint the problems asap.
  5. Hi all, just looking to tap into the broad knowledge of you all and thanks in advance. I have a pair of 30w class A maranz mono blocks, one was running intermittently cool for awhile then eventually it just ran cold. I borrowed a power consumption meter and one amp was drawing 110watts and the cold one only 9. (It still had pretty good sound btw) anyway I took the lid off and contact cleaned the only pot I could see which were the DC offset potentiometer. The amp warmed up straight away but still is only now drawing about 75 to 90 watts.. seems unstable and although much closer and sound
  6. Thanks for your reply, hope these photos help.. if needed let me know and Great! Actually Tesla was my thinking too after illiminating tungsram as my second best guess. Yes, no Telefunken diamond underneath. I wasn't sure if Phillips had a connection with Tesla but probably they owned it at some stage.. 😅 Thanks for your help, much appreciated! Oh.. it's labelled 6dj8 ecc88 bit you think it's a e88cc? That's good if it is, I believe they're a better tube..
  7. Hi all Hope this is the right place to ask couldn't find a dedicated section. Underneath the tube in center moulded into glass one tube has has a backwsrdss 7 and the other one I have an 8 Both have a 2 imprinted between the pins Any help would be great and questions welcome. Thanks, Joel
  8. yes, I've never heard of this before watching this video and you would really think it'd be something worth mentioning 😁
  9. I see, so without a load the operating point might be out. A load will just relatively change the relationship based on the starting point... And adjusting this bias will do the trick 👌
  10. Ok, I actually unplugged everything from the amp and ran them to eliminate any variables and one was hot one cold so not sure, does your diagrams depend on having a load , being the speakers or is that the amps internal bias ? Anyway I can see how it can be a variable load. Thanks, Joel
  11. Ok, that's good to know... Hopefully it's an easy fix then. 🤞 Thanks, Joel
  12. Ok, I'm not very tech savvy but I kinda thought class A was just full on all the time so bias doesn't come into it? Happy to be wrong about this and if it's just a simple adjustment I will be stoked 👍
  13. Hi all, just after a good technician to repair one of my vintage marantz mono blocks. One amp is running way hotter than the other... Not sure if it's the hot one or cool one that's the problem though, as both sound fine and they always ran hot. Anyway any recommendations for a amp guru in Melbourne would be much appreciated. Joel
  14. Hi Mike, good to get your message. I was referring to single ended inputs (unbalanced) rca. My amps are class A (30watts) push pull/ MOSFET output stage. They do run pretty hot.(good for cold winters) I'll do some research on single ended class A output stages, sounds interesting. The question originated from the attached video which stated some amps are able can convert a normal single ended signal(unbalanced) (rca) into a differential signal (balanced)using a twisted pair IC to achieve some sort of common mode noise reduction not dissimilar to true balanced gear.. a
  15. Thanks Mike, much appreciate you answer. Yes, sticking with single to single. It's all very interesting stuff, just started scratching the surface. Cheers, Joel
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