This will probably come off as a really stupid question (so i apologize for wasting anyones time in advance ) but im very new to the world of amps here and a buddy of mine gave me a 1998 Fender Roc Pro 1000 head and there seems to be something wrong with it. the symptoms are like this, the only think wrong is that you you have to turn the volume up all the way in order to hear even the slightest thing. everything powers up no problem. i took it to a local music shop here and had it checked out by someone i thought was somewhat educated in this field, and he told me that its probably not getting enough power and it would probably cost me close to $150 to get it fixed. so i figured i would come to you guys first (since you guys look like you know everything there is to know about amps ). so i did some research and determined it could be a bad power transformer. swapping that out looks like no problem but finding a replacement for it i havent yet been able to. any other suggestions? or anything else i might want to check before replacing the transformer? any advise would be appreciated. thanks in advance!
oh by the way i hope im in the right forum
oh by the way i hope im in the right forum
No stupid questions here. 🙂
Just to make sure: if there is a standby switch, did you flip it?
Are the tubes glowing? Do the big ones get hot? Careful, if they do they can be very hot when touching them.
Oh, and do you have a schematic or link to it?
/Hugo
Just to make sure: if there is a standby switch, did you flip it?
Are the tubes glowing? Do the big ones get hot? Careful, if they do they can be very hot when touching them.
Oh, and do you have a schematic or link to it?
/Hugo
Found it, in case we might need it.
http://www.fender.com/support/amp_schematics/pdfs/Roc_Pro_1000_Schematic_B12.pdf
/Hugo
http://www.fender.com/support/amp_schematics/pdfs/Roc_Pro_1000_Schematic_B12.pdf
/Hugo
Looks like I was a bit too fast about the tubes. There is indeed only one.
Consequently, there will be no standby switch.
So before I posts other nonsense, I’ll have a look at the schematic. 😉
Can you tackle basic electronics? Like checking fuses, voltages?
/Hugo
Consequently, there will be no standby switch.
So before I posts other nonsense, I’ll have a look at the schematic. 😉
Can you tackle basic electronics? Like checking fuses, voltages?
/Hugo
basic electronics i can tackle... i hope😀 do you think it could be the power transformer?? if you could guide me through what i need to check that would be awesome and a huge help. thanks hugo!
Ok, assuming you connected everything as it should be; input signal present, you fiddled with all buttons and switches and you still have no sound, take out the fuse XF1 and measure if it’s broken.
A word of warning: Don’t trust the mains switch and pull out the mains before taking out the fuse.
The second check needs mains voltage so be careful.
Check the voltage on TP23, TP24, TP26 and TP27 with respect to ground, which is CP4.
Let us know what you found.
/Hugo
A word of warning: Don’t trust the mains switch and pull out the mains before taking out the fuse.
The second check needs mains voltage so be careful.
Check the voltage on TP23, TP24, TP26 and TP27 with respect to ground, which is CP4.
Let us know what you found.
/Hugo
Try pushing a jack plug in and out of the effect return socket a few times, it could be dirty switch contacts on that?. The power supply voltages you took look fine!.
Fractured solder is the prime enemy in these amplifiers. Get out the high magnafication and start looking. The power supply caps, any power resistors, power transistors and, pots and jacks. The thermal and mechanical considerations on amplifier of this ilk are poor at best.
The jacks that fender uses in these amps are also highly suspect. The pins are quite thin and shear off. Any jacks that are normalled through, like FX send/return, may have oxidized contacts. Try running a a cable between these jacks.
Good luck to you!
The jacks that fender uses in these amps are also highly suspect. The pins are quite thin and shear off. Any jacks that are normalled through, like FX send/return, may have oxidized contacts. Try running a a cable between these jacks.
Good luck to you!
am i even supposed to be using the effect return and send? or shouldnt it just work with plugging it in the input plug.
well heres the story behind it, my freind had kept it in his closet for a couple years barely ever using it. he told me about this amp he had sitting around and asked me if i wanted it. before he gave it to me he had tested it to make sure everything was ok and it worked fine he said. when he brought it to my house last week, we hooked everything up and he was puzzled when we couldnt get any sound. just a faint sound coming out. i asked him if he had ever dropped it on accident but he said no. he just put it in his car, and drove it over ( no oopsies ) its been in his closet collecting dust. i dont get it
The effect return jack has a switch on it, that disconnects the preamp from the power amp when you insert a plug - these switch contacts can get dirty, so inserting a plug a few times can make it work again.
It's a common fault on MANY amplifiers.
It's a common fault on MANY amplifiers.
That story confirms most of testlabs's assumptions. A solder joint can crack completely with transport, so can do the jack contacts.
Time for the soldering iron, if a cable between send and return doesn't wake him up.
/Hugo
Time for the soldering iron, if a cable between send and return doesn't wake him up.
/Hugo
well connecting the cable between send/return might have done something but im not sure. it seems a bit louder but still no where near where it should be. where and how should i be looking for these cracked solders?
It takes some practice to recognise bad solderings. From the layout on the schematic I think you need to take the PCB out. This is probably going to be a though job if you are not used to it. I’m just guessing of course.
In case you want to proceed, the big resistors, the jack contacts and pots are, from my experience with other amps, the most vulnerable to broken joints.
/Hugo
In case you want to proceed, the big resistors, the jack contacts and pots are, from my experience with other amps, the most vulnerable to broken joints.
/Hugo
i think so... whats the difference?? 😱 the tube is glowing to the best of my knowledge. there isnt different intensities that it may glow at, is there? so basically if i start probing at different things and wiggling them around would that be able to indicated whether or not the soldering is bad?
Here you see the difference between mono and stereo jacks:
http://www.oselectronics.com/ose_p107.htm
Sorry for the commercial link but the pictures are clear. (Top left)
Wiring inside stereo jacks is different than in mono and often cause problems in instrument amplifiers.
If the tube glows , at least the filament voltage is OK. (12AX7, divided in two halves, top of schematic)
Gently tapping the PCB is a known technique to find bad contacts.
The handle of a small isolated screwdriver does the job.
You could try and measure a bunch of other DC values, many of them have test points (TP) but they should read VDC or just plain -16 or +40 or similar.
No use to measure VAC at the moment.
Is the solderside of the PCB visible?
/Hugo
http://www.oselectronics.com/ose_p107.htm
Sorry for the commercial link but the pictures are clear. (Top left)
Wiring inside stereo jacks is different than in mono and often cause problems in instrument amplifiers.
If the tube glows , at least the filament voltage is OK. (12AX7, divided in two halves, top of schematic)
Gently tapping the PCB is a known technique to find bad contacts.
The handle of a small isolated screwdriver does the job.
You could try and measure a bunch of other DC values, many of them have test points (TP) but they should read VDC or just plain -16 or +40 or similar.
No use to measure VAC at the moment.
Is the solderside of the PCB visible?
/Hugo
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