1969 SuperLead build - strange voltage readings

Discuss your builds of MetroAmp Kits.

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Elad E
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Joined: Sat Jun 29, 2013 9:19 am
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Re: 1969 SuperLead build - strange voltage readings

Post by Elad E » Sun Apr 26, 2015 11:39 pm

vh junkie wrote:Your first post suggested that standby was off ???
my bad - I should have stated instead that it was not set to ON.
the Metro instructions only mention to leave the amp in Standby when first checking it out prior to checking the heaters' voltage and the negative bias DC voltage - unlike the JTM 45 instructions which clearly state in bold to take the amp off standby.

I'll recheck the amp this evening.

Elad E
Senior Member
Posts: 137
Joined: Sat Jun 29, 2013 9:19 am
Just the numbers in order: 13492

Re: 1969 SuperLead build - strange voltage readings

Post by Elad E » Mon Apr 27, 2015 5:58 pm

thanks for the patience VH Junkie. I'm sorry for the misunderstanding, I'm pretty much embarrassed to have made such a mistake.
that being said - I completed the voltage inspection and biasing, fired it up tonight and it's working great!
it's very quiet - despite its being upside down without a head case, there's no squealing even when all controls are maxed out (there is a faint hint of motor boating when volume II is maxed).
I've put back the PPIMV, rebiased and it's just glorious - the range of tones available is crazy! it does clean as well as my JTM 45 (maybe a little a bit stiffer sounding with more mids instead of bass) but it can get breakup tones which the JTM simply cannot without pedals (I didn't install a PPIMV in the JTM 45 - I opted to keep it bone stock). I was afraid the PPIMV wouldn't be able to knock off enough volume for me but it's very manageable at low volumes and ir does sound very good even on the lower range of the PPIMV pot and while I can see how some people may find it fizzy, I found some great Tweed style tones hiding at the lower volume levels.

I'm also glad I incorporated a split/shared cathode switch - will probably keep it on split as it sounds much nicer with a Les Paul in comparison to the excessive darkness of the stock JTM 45 circuit with a LP (which made me believe the "Clapton used a treble booster for the Beano album" camp).

I noticed that when out of standby there is a quiet but noticeable electrical hum coming out of the area in the chassis between the snubbers, impedance selector and/or V5, V6.
is that normal? I don't remember the JTM doing that.

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