69 Superlead Build Diary

[VintageCharlie]

Thanks a bunch for the info Neil! One less thing to worry about

[VintageCharlie]

Just wondering, why do the 69 spec amps with the 50/50uF caps need them? Because of the bigger capacitance?

[harkkam08]

Hmm... 2W okay, looks like Im going to have to change them then. I think Im going to go with the CF's and leave it at 56k since ghosting might have been what gave jimi his amazing tone lol.


Right now I have 56k 1 watts in. Will that be okay or should I change them to 2 watt. I am hoping to avoiding any unneeded desoldering.

[SDM]

Right now I have 56k 1 watts in. Will that be okay or should I change them to 2 watt. I am hoping to avoiding any unneeded desoldering.

Power (Watts)= V^2/R. V here is voltage they drop, R is the resistance value in Ohms. Since these resistors are in series, they each drop half the B+ voltage at the screen node. Say you have 480V at the screen node, means each 56K drops 240V which becomes "V" in the equation. R = 56K = 56,000 Ohms. So:

Watts =(240)^2/56,000 = 57,600/56,000 = 1.029 Watts. This means each 56K resistor is dissipating 1.029 watts here in this example. Best to overrate resistors by a factor of 3 or 4 for long life/stability/safety/lower heat, but at the very least you should double the wattage the resistor is expected to see in use. So, need to use 2 watt resistors at the very least here.

Also best to use stable resistor types here, flame proof/resistant.

[harkkam08]

Right now I have 56k 1 watts in. Will that be okay or should I change them to 2 watt. I am hoping to avoiding any unneeded desoldering.

Power (Watts)= V^2/R. V here is voltage they drop, R is the resistance value in Ohms. Since these resistors are in series, they each drop half the B+ voltage at the screen node. Say you have 480V at the screen node, means each 56K drops 240V which becomes "V" in the equation. R = 56K = 56,000 Ohms. So:

Watts =(240)^2/56,000 = 57,600/56,000 = 1.029 Watts. This means each 56K resistor is dissipating 1.029 watts here in this example. Best to overrate resistors by a factor of 3 or 4 for long life/stability/safety/lower heat, but at the very least you should double the wattage the resistor is expected to see in use. So, need to use 2 watt resistors at the very least here.

Also best to use stable resistor types here, flame proof/resistant.

I figured that it probably wasn't a good idea. I swapped the one watt and put in two watt. I stopped being lazy

[harkkam08]

More Pics

I plan to swap the mustards I have in there for some wima durolits. Just to see what I get

Waiting on some pihers as well and two lemco mica's the square ones I know the red ones are not the ones used. Waiting on them.

Im going to be doing a shared cathode so the .68uf all the way to the left doesnt really come into play.

[neikeel]

I think the WIMA Tropofoils are the ones Marshall used (my 70 had them in the output 0.1s) and the earlier 68/69 50watts used 0.022uFs.

What tones are you going for?

[harkkam08]

Im going for that jimi tone. Okay NOT good. I used a light bulb limiter and everything seemed fine so I just hit the mains switch.

My reading for the heaters is 3.5V AC.

When I kick the standby switch to on I heard a pop coming from the pre-amp tube section from V1 then shortly another pop, crackle sound on v2 and I quickly shut it off.

I couldnt get any measurements in the HT mode bcuz of the pops.

Hmm.. what should I look for?

BTW the 5.6k bias resistors read -51.0V and when I turn the bias pot it goes form about -40V to -51V

The HT fuse did not blow. Plus the wiring of my Selector switch is no wrong because I flipped it so the 16 ohm pin is on the top left closet to the speaker jack because I cut the wires too short this was the only way they made it to the pins

[neikeel]

My reading for the heaters is 3.5V AC.

Is that each half (either side of centre tap ie =7vac total)?

When I kick the standby switch to on I heard a pop coming from the pre-amp tube section from V1 then shortly another pop, crackle sound on v2 and I quickly shut it off.
I couldnt get any measurements in the HT mode bcuz of the pops.
Hmm.. what should I look for?

I would fire it up without any valves in at all first and record a proper voltage chart. Popping could be absolutely anything but if it is actually coming from the board/amp with no valves then a component or connection ist trying to fail

BTW the 5.6k bias resistors read -51.0V and when I turn the bias pot it goes form about -40V to -51V

About right. Your bias circuit seems to wired ok You may need to play with the exact resistor values once the rest is up and running.

[harkkam08]

Hey guys i started another post with a voltage chart etc

I figured out the problem i had wired the bass pot wrong however im having new problems

http://forum.metroamp.com/viewtopic.php?f=28&t=34502" onclick="window.open(this.href);return false;

[harkkam08]

Hey guys I got some sound clips. Please excuse my terrible playing and I mean its terrible.

But here is what I did. I recorded 7 clips, using the mic on my macbook pro, I know its terrible but its better than nothing, however I am going to get a better mic so I can record myself and get better. Its just mindless noodling and improvising just random notes and what not.

I am using a MIM 70's reissue Strat with stock pickups with light gauge strings.

The speakers are in a 4x12 G12H 30th Aniversary x 2 and Vintage 30 x 2 16 ohm

I have mustards as my caps, the NFB is on the 8 ohm tap with 47k as the resistor. No mods or part values changed from George's kit instructions.

No pedals. Channels are jumped, plugged into the top left channel.

Using tubes that come with the kit j&j

I am using the Lar/Mar PPIMV to keep the volume at sane levels.

Let me know what you guys think about my amp.

All clips in the neck PU

Clip 1:

Using the Vintage Cable Mod here :

http://www.premierguitar.com/Magazine/I" onclick="window.open(this.href);return false; ... r_Mod.aspx

Both Vol on 2
Presence - 4
Bass - 1
Middle - 10
Treble - 4

http://soundclick.com/share.cfm?id=10234608" onclick="window.open(this.href);return false;

Clip 2:

Same Settings No Vintage Cable Mod

http://soundclick.com/share.cfm?id=10234607" onclick="window.open(this.href);return false;

Clip 3:

Same EQ settings Vol on both channels at 5 No strat Vintage mod

http://soundclick.com/share.cfm?id=10234606" onclick="window.open(this.href);return false;

Clip 4:
Same EQ settings and Vol at 5 with strat vintage mod

http://soundclick.com/share.cfm?id=10234605" onclick="window.open(this.href);return false;

Clip 5:
Vol 10 Same EQ settings as clip 1 No strat vintage mod

http://soundclick.com/share.cfm?id=10234604" onclick="window.open(this.href);return false;

Clip 6:
Vol 10 Strat Vintage Mod engaged Same EQ settings as clip 1

http://soundclick.com/share.cfm?id=10234603" onclick="window.open(this.href);return false;

Clip 7
Presence - 10
Treble - 2
Middle - 10
Bass - 1
Vol on both at 10

No strat Mod

http://soundclick.com/share.cfm?id=10234602" onclick="window.open(this.href);return false;

[harkkam08]

Hey guys just a further update I put the durolit Wima's and replaced the .018uf Mustards with .022uf Wima's and wow, the sound is so much sweeter and smoother yet has the bark of a 69 right on tap sounds much better and for some reason it has raised my plate voltage from 499 to 514 so thats a bonus, Ive re-biased and will check to see what happens.

but yeah much better than I expected I will post clips soon with the same settings.