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Post subject: Re: 1951 National 1610 by Valco
Posted: Fri Feb 17, 2017 7:08 pm
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Rock Star
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Glad you redid those coupling caps. It'll save your tubes from getting noisy from too much DC on the grids. The OD caps will last forever.


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Post subject: Re: 1951 National 1610 by Valco
Posted: Fri Feb 17, 2017 9:43 pm
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Professional Musician
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Joined: Tue Nov 27, 2012 6:56 am
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Location: Coastal Bend, Tx.
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Glad you redid those coupling caps. It'll save your tubes from getting noisy from too much DC on the grids. The OD caps will last forever.
It was an easy call once into the heater wire replacement. I will generally only play around w/ values/types on V1, but it may sound great to me as is.

Found and installed a 500pF mica cap and ran an unloaded start up w/o any issues. So the PT, fuse and on/off are all G2G. Only gave it 108 volts so the 5 & 6.3 were slightly light@ 4.7 & 3.03 ea. leg. Loaded up the tubes for a Saturday run through. Had a good dinner now its beer thirty.


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Post subject: Re: 1951 National 1610 by Valco
Posted: Sat Feb 18, 2017 9:07 am
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Nice job on the restoration. Having had to replace several coupling caps on a old silvertone radio, I know how time consuming it can be to work on these old units. But when it's all said and done, and everything still works when it's all put together, it truly is a satisfying experience.

Would love to hear some sound samples when completed, if at all possible.

Peace.

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Post subject: Re: 1951 National 1610 by Valco
Posted: Sat Feb 18, 2017 3:24 pm
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Location: Coastal Bend, Tx.
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Nice job on the restoration.
Thanks
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Would love to hear some sound samples when completed, if at all possible.
Well, my camera records video w/ sound but only a few seconds, may not be worth the trouble. I'll look into it though.

Well it fired right up as expected. Its dead quite until the very top of the volume range. It breaks up about the same on the volume knob, unless you plug in buckers.The little Rola sounds remarkably good.
The B+ is right on 300(26ma) w/ 282 @ the plates, 270 @ the screens and 14 @ the cathode of the output section.
The 6sl7 is 123.5 @ the plates and 1.42 @ the cathode
This is with the "test" tubes: Sylvania 6sl7gt, GT 6v6gt 4 rating, NU 5y3gt
Ran for about two hours w/out a single hiccup.
Cost me about $60 parts, very happy w/ the turnout.
A great little practice amp.


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Post subject: Re: 1951 National 1610 by Valco
Posted: Sat Feb 18, 2017 7:14 pm
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Glad it worked out fine. With those modern parts, the amp should last a long time
:D


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Post subject: Re: 1951 National 1610 by Valco
Posted: Mon Feb 20, 2017 10:55 pm
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Location: Coastal Bend, Tx.
As far as a sound clip goes on my camera, its about 1Meg per second of audio and not feasible to record with.
If I come into any easily expendable cash, I may look into a recording device down the road.
Apologies for the HBO type porn.

It is a sweet little 7 watt amp though and sounds really good to my ears w/ the original RCA tubes back in the sockets. Very balanced maybe slightly bright on the bridge pup w/ the tone dimed on the Strat. Back off to about 8ish on the tone control and its just right. My Heritage bridge humbuckers sound aggressive through this amp, very tight low end polished mids and highs w/ good note separation. It has a good amount of gain and breaks up nicely above about 8, if it had numbers on the dial.
I dropped the 1st electrolytic capacitor value from 40uF to 30uF to match the original schematic and believe it adds a little bit of sag to the output section. There was no output stage electrolytic bypass capacitor in the amp or on the schematic. Adding one would probably boost the output sections response dynamics.

Also a note about my previous post concerning the voltages in the amp; I ran through the Brown Box @ 112-113 Vac. Increasing the voltages higher would likely result in a slightly more pronounced sonic variance of the above description. I would feel comfortable plugging into 120 but not much higher w/o testing the entire circuit again.


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Post subject: Re: 1951 National 1610 by Valco
Posted: Mon Feb 20, 2017 11:31 pm
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Looks like it was a good R&R fix. Tone description does remind me of those early Fender cathode-biased push-pull amps.

;)


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