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Post subject: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Tue Apr 03, 2018 7:02 am
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My trusted Fender Pro Reverb on day wouldn´t power up. No light on the pilot light, no heat in the tubes and no hum. My first thought was the main 3A fuse. It looked good, but I changed it anyway. And I changed the 0,63 AT fuse for the standby. But still nothing...

I opened up the amp, and I could se a 6,3AT fuse connected to the wire to the pilot light. That was blown. So I changed that fuse as well. I also changed the two power tubes. But still nothing happens when I try to power up the amp. No fuses blow, no pilot light (the bulb looks good) and no hum. Please help!!

Thor


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Post subject: Re: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Wed Apr 04, 2018 3:58 pm
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If all fuses are ok , are you really sure ?
Looking fuses by eyes is not enough, you need a meter. Or put all new fuses.

Keep power tubes out of the amp, power amp ON , see if pilot lamp glow ,
Short power tubes may be a issue

Report


If nothing glow , amp must see a tech


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Post subject: Re: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Wed Apr 04, 2018 6:04 pm
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+1 on the MM. Some voltage readings can at least get you turning down the right street.

UN


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Post subject: Re: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Thu Apr 05, 2018 8:34 am
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You may have a rectifier tube shorted, since you had a blown fuse.
Check power outlet at the wall.
Remove "all" tubes. Plug in and power on, keep the speaker connected(a good habit).
With meter check all power transformer secondary AC voltages. If you have appropriate readings at lamp(6.3V), on/off/standby(120ishV) and rectifier pins(2&4-5v,4&6-375ishV). If the transformer is working properly, power off and insert a rectifier tube.
Power up and re check voltages of rectifier pins AC & DC, B+, output plate supply, heater supply to all pin sockets, lamp and fuse's. If no faults are found w/ the rectifier, power off and insert output tubes.
Continue in this fashion through out replacing all the tubes, identifying and fixing issues as they appear circuit by circuit.
voltages above from AA1069.

Assuming you are going to attempt to DIY. Be careful, there's enough voltage to kill you-dead!
A good tech could probably troubleshoot the amp w/in 15-30 minutes for a reasonable price in most cities.


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Post subject: Re: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Thu Apr 05, 2018 8:54 am
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+1 for rectifier tube,

thorlonning, don't forget Power tubes too

1-Remove those 3 tubes ,
2- put know good fuses . Power amp On

3- If fuses don't blow , ( check each one carefully ) put rectifier tube
4- If fuses don't blow , ( check each one carefully ) one power tube
5- If fuses don't blow ,( check each one carefully ) put second p.t.

One or more fuses must blow between 3 and 5 test , replace tube


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Post subject: Re: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Thu Apr 05, 2018 11:36 am
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Somebody needs to go back to school for a remedial course in 'Fenderology'.

:lol:

The Pro Reverb Amp of 1979 has no rectifier tube. It's an ultra-linear platform of 70 watts output, just as with the UL Super Reverb and UL Bandmaster Reverb. Rectification is accomplished via a solid-state diode stack.

That the amp's pilot lamp is not lit and all the tubes are dark is a good indication of a problem with the power tranny's 6.3 VAC tap. A voltage check of that secondary winding will quickly confirm it.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Thu Apr 05, 2018 2:40 pm
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Yeah see, we still need ya around here for sanity sake Arjay.

I shouldn't make excuses but I don't have schematics past the early 70's, but I was on the right track.


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Post subject: Re: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Thu Apr 05, 2018 6:36 pm
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I'm quessing its further upstream in the ac primary. Cord, switch, fuseholder , or worst case, the power transformer.
Glad you're watching over us Arjay.


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Post subject: Re: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Fri Apr 06, 2018 1:31 am
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Could be power cord. I'd get a DVM and do some VAC measurements.


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Post subject: Re: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Fri Apr 06, 2018 1:33 am
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[quote="Retroverbial"
That the amp's pilot lamp is not lit and all the tubes are dark is a good indication of a problem with the power tranny's 6.3 VAC tap. A voltage check of that secondary winding will quickly confirm it.

Arjay[/quote]

OP write ;
" I could se a 6,3AT fuse connected to the wire to the pilot light. That was blown..... "

Look is not the Power Transformer


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Post subject: Re: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Fri Apr 06, 2018 1:34 am
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BMW2002Ti wrote:
Could be power cord. I'd get a DVM and do some VAC measurements.


Power cord can not blow fuses ,


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Post subject: Re: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Fri Apr 06, 2018 6:15 am
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I don't know, call me simple but...........a "simple" check to see if there's voltage to the PT primary and the correct voltage coming from the 6.3v windings would clean up speculation. I know that's been mentioned but it needs to be confirmed.

UN


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Post subject: Re: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Sat Apr 07, 2018 11:04 am
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A simple way to check the primary for a non-techie is to unplug the amp, turn it on and put a 9 volt battery across the pins of the ac plug. Do it in a dim location. If there is a little spark then you touch both contacts to the ac plug, the primary circuit is OK.
Looking at the schematic, I don't see a fuse connected to the pilot light. I see a 4.7 ohm resistor. If it was blown, it would stop the pilot light, but the tubes should still light.
Maybe the op isn't sure of what they're looking at.


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Post subject: Re: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Sat Apr 07, 2018 11:11 am
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TimsAudio wrote:



Maybe the op isn't sure of what they're looking at.



+1000


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Post subject: Re: FENDER PRO REVERB 1979 NO POWER AND PILOT LIGHT ISSUE!!
Posted: Mon Apr 09, 2018 6:50 am
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TimsAudio wrote:
A simple way to check the primary for a non-techie is to unplug the amp, turn it on and put a 9 volt battery across the pins of the ac plug. Do it in a dim location. If there is a little spark then you touch both contacts to the ac plug, the primary circuit is OK.


This is a nifty trick, for on-the-road quick diagnostics. Thanks!


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