Mindprint Envoice humming while effects turned on?

Hi guys! I'm new here and hope anyone can help me with this!

I got this preamp as a present from a colleague. But I recognized there is a low frequency humming (around 100 Hz) when I turn on the effects section. He said he never heard this before but he also didn't use it for a long time.
As I don't have any skills in electricity/tube stuff I can't really work on the inside of the preamp. But I asked myself if it could be the tube which is not working anymore and then produce such a humming?
I also recognized that when I press on a certain location on the top of the amp or if I hold it in the hands and move it around the humming disappears for a few seconds but always comes back then.

I'd google mindprint groupdiy or vice versa and see if you can find anything helpful while waiting for others to jump in??
Here's one thread for example.....

https://groupdiy.com/index.php?topic=7173.0

scott2000 said:

I'd google mindprint groupdiy or vice versa and see if you can find anything helpful while waiting for others to jump in??
Here's one thread for example.....

https://groupdiy.com/index.php?topic=7173.0

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Hey thanks for our reply. I googled and I found two threads within this forum (that's why I registered here) but as I wrote I have no clue about electricity and stuff so I feel not comfortable to open the preamp and 'see' whats wrong or what parts maybe have issues and fix them.. maybe it's the wrong forum then I don't know :O
I hope there is someone out here who knows such a problem (humming noise in tube preamps) and maybe just say then 'yes it's the tube, change it' or 'no, go to a shop to get it repaired' and so on

Xilef said:

Hey thanks for our reply. I googled and I found two threads within this forum (that's why I registered here) but as I wrote I have no clue about electricity and stuff so I feel not comfortable to open the preamp and 'see' whats wrong or what parts maybe have issues and fix them.. maybe it's the wrong forum then I don't know :O
I hope there is someone out here who knows such a problem (humming noise in tube preamps) and maybe just say then 'yes it's the tube, change it' or 'no, go to a shop to get it repaired' and so on

Click to expand...

If you aren't comfortable with electronics, maybe post your location and others here may be around you who could refer someone or help?

Hard to say if it would be tube related.  Could be an interconnect  or jack issue,
(like the thread I linked mentioned about the insert jack and some other issues) ,  or could be some type of other ground loop causing it???. Could totally  be something else that would require getting in and messing around with electricity to find out

...Although, even with the unit unplugged, there's always a chance of getting electrocuted from something holding a charge inside so, be aware!

Good luck....

I've repaired two of those. The first thing to check, is the power supply. Due to it's age and the heat inside the unit, the capacitors MIGHT be faulty.

Also, it's always good to clean the connectors, especially if the problem is in channel 1. Channel 2 usually gets less use.

it could of course also be an outside ground issue, so check cabling.

Thank you for all the answers! I will check if I can do something myself or if I should take it to a repair store.

hi, just bumped randomly on this topic, both of m mindprints pursed around 2002 had this problem, inboth it was the 400 capacitors that were "tired"

costed me 10-15 euros and they are back like new ( if it can help )