Crate G212 question

[Mace Hacker]

What are the correct values of the diodes shown in the pictures, and what is the proper way to install them? I got this amp from a kid in my neighborhood and he had tried to replace the diodes with some he got from somewhere. I don't know. The ones on the board are not the originals and I don't know which way to face them when I do mount them.

[DJPhil]

Good photos, is always nice to have pictures to work with.  :tu:

I went to Crate's site and they've got the manual for download, which contains a schematic. The last page has the power section, and the diodes in question are D6 through D9. The band on the diode case is the cathode, and goes to the more negative side of the connection in normal operation. The schematic symbol points in the direction of the cathode, and the short line at the end of the triangle is on the same end as the band on the case. That should help you sort out the orientation, just trace the circuit and double check as you go.

Those look to indeed be the rectifier diodes, which they specify as 1N5392 (datasheet). These are available for something like $0.03 to $0.07US from various distributors like Digikey and Mouser. Essentially any diode with similar ratings should work, the important specs are 100_Vrrm and 1.5_IF(AV). These can handle about 30% more continuous and peak current than a 1N400X series diode, so those should not be used.

With some creative wiring and a little space you could use a chassis mount rectifier (about $5US) to replace all four diodes. This is what I would do, though many would say this is overkill.

This should sort out the diodes, cross your fingers and hope nothing else got roasted.

Hope that helps.

[J M Fahey]

Fully agree with DJPhil and add: just as a double check:
in two of those diodes, D6 and D7, the white bands join the positive end of C15 and the metallic case of Q9, easy to check with your multimeter on the diode check setting, even more if it has a buzzer to show continuity.
Similarly, on D8 and D9 the non-band ends touch the negative side of C16.
It's the same as what DJPhil said, but in a little easier mnemonic way when you are testing.
Good luck.

[Mace Hacker]

Outstanding. Thank you very much, both of you, for the input. I had looked at the diagram from Crates website but, it show up very fuzzy on my pc. Hard to read it.

                                                                                            Cheers,
                                                                                                        Mace Hacker
PS: Will post pics of finished project.

[DJPhil]

The picture is definitely a bit fuzzy, it's a bad scanning job. I've found it's way faster and easier for me on those to squint than try anything fancy with graphics programs.

Definitely keep us posted.

[Mace Hacker]

Well, for me, I need clear and easy. My background in electronics is limited. Even with your answer from above I will have to look and compare values or get my friend to look at your answer and tell me what diode exactly I will need. LOL I have mostly been been a bench monkey for my friend. He's had classes in electronics repair and has had a business before repairing  stereos, amplifiers, ect. I have often helped him by doing things like; cleaning boards with corrosion, resoldering connections, desoldering parts and replacing them, ect. I have built simple circuits on veraboard and bought Prefabbed PCB projects.  So if I can't read a diagram clearly and figure out the value and correct positioning of a part easily, I call him, or post questions in forums like this. If I see an obvious problem I fix it. If it still doesn't work I take it to my friend for help.