I've recently bought a McIntosh mx110z that still has the old selenium rectifiers id like to take precautions in changing them out with silicone diodes but am inexperienced in how it should be wired with a diode bridge if anyone has an example I could follow any help would be appreciated. A few main questions I have is what the voltage should be coming from the rectifier so I know how much the drop down voltages should be and also with the preamp having a full wave and half wave rectification are these part of the same rectifier or are they separate from each other. Any help is appreciated.
Mx110z selenium rectifier replacement
- Thread starter PLUTD
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There are 6 diodes in the power supply - D11, 12, 13, 14, 15 and 16 and they're clearly shown on the schematic. Flip it over, take the bottom off and check your voltages. Check volts at C114 where it connects to D11 and 12 and R147 (1.5k, 2W); it'll be around 300v. Write that one down then check the rest of the volts on the schematic, 225v, 170v, 155v and 83v. All of the tubes should be installed.
When I did mine, I just used 1n4007 to replace the seleniums but others here suggested that 2 amp diodes would be better. The voltages will go up about 10% or more so consider adjusting the resistors in the power supply. I never did.
If you want to install a bridge rectifier, that should work too but you'll have to figure that out.
Murray
Edit: Not very good at counting so I fixed that.
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Have you noticed any performance difference with the added voltages in the unit and do I check the voltage off the capacitors or from the leads. Thanks again any information helps a lot.
Sorry for the late reply. I changed pretty much everything - 'lytic caps and all new tubes so it likely would sound somewhat different. But, if your voltages are low, I suggest that you look into why and fix it.
Murray
Here's photo of mine. Also, read the attached post from dcgillespie.
Attachments
Thanks for the information it's more than what I've been able to find on the situation. Is this a proper example of how the diode bridge should be made?
Yes, that is correct.
Hi, I have the same issues, where are you connecting the 100 ohm resistor, my voltage is too high and replace the r148 by 2.2 instead of 1.5, but still high.
Thanks
I added a small terminal strip to the back screw of the power transformer and attached the 100 ohm resistor there. I'm attaching a detailed photo of my overall setup.
Attachments
Thanks for the picture, my voltage is way too high!
Where is the red attached to the 100 ohms resistor coming from, was is the one connected to the 2.2 ohms/ 5 watts ?, I have a yellow and a red in there.
Thanks again
Where is the red attached to the 100 ohms resistor coming from, was is the one connected to the 2.2 ohms/ 5 watts ?, I have a yellow and a red in there.
Thanks again
Yes thanks, that should lower the voltage to the original value?
I will try that, thanks again!
Have you also changed the power capacitors and can you also show pictures of how you're going about it.
yes I changed all the power caps, from Hayseed, I order the resistors and will do it next week and post a picture.
Do you know where to find a glass for the mx110z, the lettering is completely off, radio daze never answer email or phone, not sure if they are still around!
Thanks again
Do you know where to find a glass for the mx110z, the lettering is completely off, radio daze never answer email or phone, not sure if they are still around!
Thanks again
Supposedly if you call McIntosh they can help you out with vintage replacement parts but never tried myself
McIntosh Parts does support vintage McIntosh to the extent that parts are still available, and IMO some parts are reasonable where others are a bit high, usually I start there when getting into a project and find that I “need” more than I started with. Bulbs (for example) have been high, but I trust the quality/longevity, semiconductors are sometimes high but there are many that are specially screened so again I trust that they are the proper part vs the industry standard version (found that out “the hard way” buying the industry OEM part and it oscillated). Also love to support the factory and they have good information on what is correct.
Second choice is usually Audio Classics. I have seen some NOS parts that McIntosh had many in stock, then none, and Audio Classics had them instead. Likely a simple matter of AC bought out the stock of certain parts that they feel that they can use or sell in the future. A couple of other sellers also have OE parts, the McIntosh Compendium has a page devoted to those.
In the end, it’s a corporate world where many people sell parts and the internet makes it easy to buy cheaper, which is why you seldom find little highly-knowledgeable hardware stores etc. anymore, so I prefer to do my best to support McIntosh Parts so that it makes enough money for them to continue, same with AC and others.
Second choice is usually Audio Classics. I have seen some NOS parts that McIntosh had many in stock, then none, and Audio Classics had them instead. Likely a simple matter of AC bought out the stock of certain parts that they feel that they can use or sell in the future. A couple of other sellers also have OE parts, the McIntosh Compendium has a page devoted to those.
In the end, it’s a corporate world where many people sell parts and the internet makes it easy to buy cheaper, which is why you seldom find little highly-knowledgeable hardware stores etc. anymore, so I prefer to do my best to support McIntosh Parts so that it makes enough money for them to continue, same with AC and others.
