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Hoffman Amps Forum image Author Topic: Harmony H415 problems, help!  (Read 14963 times)

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Offline sluckey

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Re: Harmony H415 problems, help!
« Reply #50 on: December 21, 2018, 07:09:12 pm »
100pF (pico farads)
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline string bender

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Re: Harmony H415 problems, help!
« Reply #51 on: January 01, 2019, 05:45:36 pm »
Sucess today!!!! and on the first day of the new year.

Yesterday I wired my input jacks/wiring per Hi/Lo inputs. I had to figure out the Harmony jack, a plastic self grounding input. You remember I had "anemic" sounding input channels.
Last night I realized that I may have installed wrong parts.
Early this morning I awoke and removed a resistor on the input and discovered it was missing a "K" behind the value 68 ohms.
Oh the meaning and difference of a subtle mistake.

I am very pleased with the rebuild and sound quality and tomorrow I will re install the chassis.
Ok onto the next project: removing the harshness of toneality when going past 3 on a 1995 Fender Custon vibrolux reverb (Mike Moyer mod).
If that is sucesful I will attempt a "revibe" hum issue on my clone tremolo/reverb that was a copy of Cesar Diaz tank.

For those that took time to help me in this exercize I am very thankful. It feels quite rewarding to accomplish basic amp repair. I thought this day would come, never thought it would take this long however. All good.

Regards
Doug

Offline string bender

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Re: Harmony H415 problems, help!
« Reply #52 on: January 02, 2019, 05:51:58 am »
Thought I could put the chassis back in the cabinet today but I'm dealing with a 60 cycle hum.
Not sure what to do.

I took out V1 tube and V2 each one did not make this go away however V2 tone was changed it is still 60 cycle measured on my tuner.
It is effected by volume.

Any suggestions?

Offline shooter

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Re: Harmony H415 problems, help!
« Reply #53 on: January 02, 2019, 07:02:36 am »
Quote
still 60 cycle
so it's left of vol, probably inductive coupled to the sig path, but slim2none, a bad tube.  tried putting your box in a bigger metal box, move it outside, re-route wires, start on left and pull tubes til it's gone, or you're down to PA tubes only
Went Class C for efficiency

Offline John

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Re: Harmony H415 problems, help!
« Reply #54 on: January 02, 2019, 07:53:31 am »
Unless it's a lot worse than mine, you'll never hear it when you're playing. They're running the heater wires right past everything else, so you'll pick up some of that. IMO, no biggie.
Tapping into the inner tube.

Offline shooter

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Re: Harmony H415 problems, help!
« Reply #55 on: January 02, 2019, 08:39:38 am »
Like what John said, my hum test; if it can't be heard when my guitar is on 1, I sleep well
Went Class C for efficiency

Offline string bender

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Re: Harmony H415 problems, help!
« Reply #56 on: January 03, 2019, 11:28:21 am »
Through the advice of one of blog members I "created an artificial center tap on the heaters".
This resolved the harshness tonality of the 60 cycle hum.

Fix: from the extra 68 ohm resistors that I had I put one from V4 pin 3 to pin 4, and one from V4 pin 3 to pin 5.
I removed the ground from V1 pin 9.

The amp sounds really good. I am not thinking of unloading this but possibly my go to amp among the family in my collection.
I would like to use this to play out, use in conjunction with my 63 reissue reverb tank and possibly pedal board but honestly you only have to run a higher volume on the amp and use your volume/tone knob on your guitar to get some saturated "leads" that I believe will cut through the mix. At 18 watts I gather this is a similar amplifier to the "Marshall 18 watt tone that many famous guitarists have used in the past".

I'm totally satisfied at this being my first experience of tube amplifier repair and it would not have been possible without the fine group of people that have helped me through this.
I gained knowledge in reading schematics and feel quite knowledgeable about the layout on this H 415, however I do lack the understanding of "how it all works" and like understanding music theory I gather this will be challenging for me however its a thrill to be able to converse with more knowledgeable people on this forum.
Thanks for making this an enjoyable 1st.
Regards
Doug  :icon_biggrin:

Offline John

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Re: Harmony H415 problems, help!
« Reply #57 on: January 03, 2019, 07:42:36 pm »
Glad it turned out so well!
Tapping into the inner tube.

 


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