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Post subject: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Sun Mar 05, 2017 1:20 am
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I've had this amp for many years. I love the way it sounds so I never replaced anything. Last night i played for 2hrs or so and the amp was fine. I turned it off for about 30 mins. When I went to turn it back on again the fuse instantly blew. I went to radio shack and got 2 amp slow blow fuses and now the amp keeps blowing them out after 10 to 20 seconds of being on stand by. I blew 2 fuses I figure I'll stop trying until I get some advise.


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Post subject: Re: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Mon Mar 06, 2017 2:23 am
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You may have one or more output tube blow.

Use only 1 ampere Slow Blow fuse, not Fast blow and no more than 1 ampere

1-Remove all 6V6s, put a new fuse and power amp ON.
if fuse did not blow, put news 6V6's, and check bias.

2- If fuse blow, remove rectifier tube GZ34 , put new fuse.
Power amp ON
If fuse did not blow, you may need a new GZ34 or filters caps or.....

3- If fuse blow you have to check Power transformer.


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Post subject: Re: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Mon Mar 06, 2017 2:29 am
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stratele52 wrote:
Use only 1 ampere Slow Blow fuse, not Fast blow and no more than 1 ampere


+1000!

The fuse is there to protect the amp from calamity, which yours has apparently suffered.

Over-spec the fuse and you risk further damage.

Follow Stratele's recommendations for troubleshooting and if the issue cannot be isolated and identified as a defective tube, find a qualified amp tech.

Arjay

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Post subject: Re: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Mon Mar 06, 2017 5:59 am
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Very good diagnostic strategy. BTW... the SF DR takes a 2-amp Slo-Blow, in case you already bought a bunch of fuses. The BF DR takes 1-amp. I have no idea why there is a difference. :?:

SF:
https://cdn.shopify.com/s/files/1/0202/ ... 1411075540

BF:
http://www.folkwaymusic.com/images/inst ... -panel.jpg


Last edited by BMW2002Ti on Mon Mar 06, 2017 9:54 am, edited 1 time in total.

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Post subject: Re: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Mon Mar 06, 2017 7:16 am
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BMW2002Ti wrote:
BTW... the SF DR takes a 2-amp Slo-Blow, in case you already bought a bunch of fuses. The BF SR takes 1-amp. I have no idea why there is a difference.


Another of those enigmatic Fender anomalies. The AA763 and AB763 schematics for the Deluxe Reverb specify a 1-amp fuse but the rear panel of my 1968 model is marked for a 2-amp. The schematic was finally altered in August of that year when the AB868 revision appeared with an "official" change to the 2-amp type.

Arjay

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Post subject: Re: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Mon Mar 06, 2017 12:10 pm
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BMW2002Ti wrote:
Very good diagnostic strategy. BTW... the SF DR takes a 2-amp Slo-Blow, in case you already bought a bunch of fuses. The BF DR takes 1-amp. I have no idea why there is a difference. :?:

SF:
https://cdn.shopify.com/s/files/1/0202/ ... 1411075540

BF:
http://www.folkwaymusic.com/images/inst ... -panel.jpg


Thank's for the information.


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Post subject: Re: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Mon Mar 06, 2017 1:46 pm
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I may have a reason for the fuse discrepancy between blackface and silverface models.

Using the simple "PIE" equation (Power = Current x Voltage) the blackface's 1-amp fuse is correct.

120 watts (power consumption) = 1 amp (specified fuse) x 110 volts (extant primary voltage).

As the silverface era began, wall-socket voltages began creeping upward to 115 volts then 117 volts and finally 120 volts (even higher in some locales). The original 1-amp fuse had no surge margin for normal transient demands. Thus, Fender uprated the fuse to reflect those input voltage changes.

Arjay

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Post subject: Re: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Mon Mar 06, 2017 1:49 pm
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+1 :)


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Post subject: Re: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Mon Mar 06, 2017 2:28 pm
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It's the only thing I could think of but if anybody else has an idea or two, let's air them out and see if anything else adds up.

Arjay

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Post subject: Re: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Mon Mar 06, 2017 2:50 pm
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The only thing I can think of (for fuse change) --- and this is a big WAG --- the BF era DR used GZ34 rectifier. The later SF era DR switched to 5U4GB.

The 5U4GB draws 3 amps of current. The GZ34 draws less. But, still more than 1 amp. Oh well... told you it was a WAG. :lol:


Last edited by BMW2002Ti on Mon Mar 06, 2017 9:30 pm, edited 2 times in total.

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Post subject: Re: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Mon Mar 06, 2017 2:57 pm
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That might make sense since the 5U4GB was first specified in the AB868 revision (the silverface AB763 used a GZ34 but is spec'd for a 2-amp fuse).

Arjay

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Post subject: Re: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Wed Mar 08, 2017 10:33 pm
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Thanks so much for the info guys! Lots of interesting stuff here. I just got a pack of 125v 2amp slow blow fuses today. I have a new rectifier tube coming in the mail as well. I will try these troubleshooting methods tonite. Thanks again!


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Post subject: Re: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Thu Mar 09, 2017 2:09 am
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Johnnypopsickle wrote:
Thanks so much for the info guys! Lots of interesting stuff here. I just got a pack of 125v 2amp slow blow fuses today. I have a new rectifier tube coming in the mail as well. I will try these troubleshooting methods tonite. Thanks again!



And if you need only Output Power tubes ?

Why don't you do the tests / trouble shooting before ordering tubes ?


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Post subject: Re: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Fri Mar 10, 2017 3:12 pm
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Retroverbial wrote:
It's the only thing I could think of but if anybody else has an idea or two, let's air them out and see if anything else adds up.

Arjay


My theory is it was done to account for the export models, operating at 220v, being shipped overseas.
:oops:

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Post subject: Re: 1969 silverface deluxe reverb amp keeps blowing fuses
Posted: Fri Mar 10, 2017 7:51 pm
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Abe, actually the higher the outlet voltage, the less current as amp needs to work. It's a wattage thing.

Work (watts) = Voltage times current.

Volts double, current half = same watts.


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