The fender 85 combo is a solid state amplifier with 85Watts of power, a 12" fender speaker, 2 channels, EQ, spring reverb, fx loop, headphones out and footswitch. It was made in the USA back in 1987!There were actually 3 models produced at the time: the eighty-five, the 85 studio and the 85 deluxe combo. Mine is the simple 85. It's very similar to the studio 85 but the deluxe model is quite different. There are the studio and deluxe schematics online and via Fender support (if you wish to send them an e-mail). Here they are:
http://music-electronics-forum.com/attachments/4454d1234452179-fender-studio-85.jpg
http://www.fender.com/support/articles/fender-guitar-and-bass-amplifiers-owners-manuals-and-schematics-hard-copy-archives/
http://www.scribd.com/doc/27558787/Fender-Deluxe-85
I used the studio 85 schematic for my 85 combo. The main problem with these amps is overheating... The pcb was almost fried in my case and I replaced all the power resistors and supply capacitors. Then, I rearranged things inside the amp to keep heat-producing elements as far apart as possible (power amp, transformer, resistors etc), I would also be a good idea to open up a window at the back of the amp and install a small PC fan to cool things up.
This amp was covered in dust and had two broken jacks: the High Input and the Preamp out (aka fx send) one. All the pots were scratchy and noisy plus there were a few old parts that were overheating inside. These issues are common with amplifiers of this age and there are ways to address them.
First I opened the amp up and gave it a good clean up. Once it was dust free, I used some wd40 to clean a few rusty spots on its metal chassis. The pcb was cleaned with compressed air and the pots/jacks were sprayed with oil-free contact cleaner.
Then, I unsoldered the old broken jacks and a few power supply components that were worn out. The psu (power supply) had a few 10W ceramic power resistors, capacitors and diodes that turned brown. Some pcb areas and traces had burn marks on them. I used jumpers to make up for the crispy and rusty pcb traces and I replaced all the almost burnt psu components with brand new ones!
Note: if your amp produces excessive 50-60Hz hum, it's usually due to supply capacitor failure. I would suggest you to replace the large caps and ceramic resistors and resolder the pcb traces/pads with signs of burn/overheating.
After replacing all the faulty components, the amp worked like a charm and the tones available are quite good. There's the classic fender clean channel for clean and surf rock tones plus the OD channel with compression(limiter), gain and boost controls than produces from light od/fuzzy tones to hard rock/metal gain. It's quite a versatile amp and tone-wise I prefer this one to the latest frontman series amps.
Here are a few pictures of the fender 85 combo:
Cheers,
Thanos
hi thanos you wouldnt have the schematics for this amp would you ? i have a fender 85 just failed it just hums when switched on thanks pat.
ΑπάντησηΔιαγραφήHello Pat,
ΔιαγραφήThere were actually 3 models produced at the time: the eighty-five, the 85 studio and the 85 deluxe combo. Mine is the simple 85. It's very similar to the studio 85 but the deluxe model is quite different. There are the studio and deluxe schematics online and via Fender support (if you wish to send them an e-mail). Here they are: http://music-electronics-forum.com/attachments/4454d1234452179-fender-studio-85.jpg
http://www.fender.com/support/articles/fender-guitar-and-bass-amplifiers-owners-manuals-and-schematics-hard-copy-archives/
http://www.scribd.com/doc/27558787/Fender-Deluxe-85
I used the studio 85 schematic for my 85 combo. The main problem with these amps is overheating... The pcb was almost fried in my case and I replaced all the power resistors and supply capacitors. Then, I rearranged things inside the amp to keep heat-producing elements as far apart as possible (power amp, transformer, resistors etc), I would also be a good idea to open up a window at the back of the amp and install a small PC fan to cool things up.
Excessive hum is usually produced by supply capacitor failure. I would suggest you to replace the large caps and ceramic resistors and resolder the pcb traces/pads with signs of burn/overheating.
Cheers,
Thanos
hi thanos thank you for your quick reply .i have changed all the caps the 2200 uf 50v x2 and the TIP 147 and TIP 142 also all the other smaller caps my amp is the same as yours its the simple 85 all the ceramic power resistors are sound and reading fine on the meter all joints have been reflowed i have also checked all power resistors .the only thing i have still to check are the 4 rectifiers .but i have no blown fuses .i am beginning to think its a transformer fault ? i will check rectifiers and let you know of any progress i would like to get this going but if its the transformer dont know what that would cost to buy ? thanks again regards pat.
ΔιαγραφήOk, so you've taken most restoration steps. You should measure the transformer voltages by disconnecting its secondary from the pcb. Read these AC voltages. If all is good and symmetrical to the center tap, it's not the transformer. Next, plug the t/f back on the pcb and check the DC rail voltages. Maybe the rectifiers have overheated and failed. I would certainly replace the resistors as well. They read Ok on the multimeter but you can't really see what's going on when they overheat and if their thermal noise is now over the top... Hum could also be a sign of internal oscillation. E.g. an audio path chip or transistor (used as a filter) oscillates and produces loud audio hum. Chip aging or Capacitor and resistor value drift can cause such things.
ΔιαγραφήI hope you get to the bottom of this!
-Thanos
thanks thanos i will go through that process and let you know the outcome you have been very helpfull regards pat speak soon .
Διαγραφήhi thanos a wee question are the 3 ceramic resistors point .47ohm or just 47 ohm thanks again pat.mines are a bit smudged .
ΔιαγραφήHello!
ΔιαγραφήThe three R84, R85, R88 5W resistors of the power amp are just 0,47 ohms. These are part of the power amp circuit load so it's good to replace them. I did replace them with 0.47ohm/10W ones. The R84, R85 pair has to be matched (their resistance values should be really close). Mismatching of these resistors could cause noise issues.
Cheers,
Thanos
hi thanks again thanos i will let you know the end result when completed regards pat.
Διαγραφήhi thanos a small prob i cleaned everything up i took the TIP 147 and the TIP 142 off the board again to clean the solder work up .now i cant remember where they go Q2and Q1 marked on the panel dont know what goes where the schematics i have are all blurry .was just going to power it up thanks again thanos regards pat.
ΔιαγραφήHello Patrick,
ΔιαγραφήBased on this schematic: http://music-electronics-forum.com/attachments/4454d1234452179-fender-studio-85.jpg
The Q1 transistor is the NPN type one, so it is the TIP142 !
To be 100% sure this is the Q1-labeled transistor of the schematic,
check the PCB and see if Q1 is connected to CR27, CR29 and R80.
Then, Q1 is Tip142 and Q2 is definitely Tip147.
Cheers,
Thanos
Thanks for that again thanos will check that out and see how it goes from there i will still report any progress with this amp. regards pat
ΔιαγραφήThanos.
ΑπάντησηΔιαγραφήwondering if you have the dimensions/measurements of the Deluxe 85 chasis. I have an empty 1x12 cab with speaker and I want to put a Deluxe 85 into it.
Hello! Unfortunately, I haven't measured its dimensions. You could however try to place the deluxe 85 chassis inside the cab you have and see for yourself. If you don't own the 85, just ask the seller to measure it for you prior to buying it.
ΔιαγραφήCheers, Thanos
Hi,
ΑπάντησηΔιαγραφήHow do you remove the amp from the chassis? I have unscrewed the handle and the 4 screws on top and the amp will not budge!
Hello and thanks for reading my blog!
ΔιαγραφήI am pretty sure this amp has two side screws as well. Undo these screws on the sides and the chassis will be free. Wiggle it a bit as there is usually a bit of tacky material glued between the cab and the chassis to eliminate vibrations.
Hey, great blog. I own the Deluxe Eighty-Five combo, and am experiencing sporadic volume dropouts and serious scratchy/fuzzy in both of the main inputs. I have ruled out the speaker. Will simply replacing the input jacks address this issue, do you suppose? Or is it possibly a deep-seated issue? Do you have a link to the correct input jack part by chance? Thanks!
ΑπάντησηΔιαγραφήHello and thanks for reading my blog!
ΔιαγραφήIt could be and fx loop issue. Try plugging a guitar cable from the preamp out to power amp in jacks. If the problem goes away the fx loop jacks have to be cleaned with contact cleaner spray or better yet replaced. Spray the input jacks as well. The in jacks are quite hard to find ,maybe fender can help out. They can certainly be replaced with simpler modern jacks and a few jumper wires by a qualified tech if he/she studies the 85 schematic.
Cheers,
Thanos
Hi Thanos, Thanks for all the useful information. I have an eighty five that’s in rough shape. Input jack 1 broke off last weekend. Do you have the parts list for your restoration? Would love to know which jack to order and may take a look at the caps and solder joints while I have it open.
ΑπάντησηΔιαγραφήCheers
Jim
Hello and thanks for reading my blog! These fender input jack are pretty weird and most of their pins are not even used... I don't have an 85 parts list but here's the deluxe85 list. Input jacks should be the same: https://medias.audiofanzine.com/files/fender-deluxe-85-parts-list-471707.pdf , https://elektrotanya.com/fender_deluxe-85_parts-list_sch.pdf/download.html
ΔιαγραφήThe only reasons why these multi-pin jacks are used are the "mute" signal for the U6A selector and the attenuation of the 2nd input. A regular amp design would simply short the input to ground when no plug is inserted...
Cheers, Thanos
Hi Thanos. Thanks for your post and links as I've got myself a North American Fender 85 that I'm trying to fix up.
ΑπάντησηΔιαγραφήI could use your advice in restoring my amp. It works, however the output of the amp is not clean. If I go through either of the inputs with the OD channel off, there are definitely unwanted frequencies being heard. It doesn't matter what volume I play at, quiet or loud, little gain, full gain, etc.
I've also bypassed the input and gone straight into the power amp input channel and it still does not sound clean; even straight from my guitar.
Any ideas on what it could be? The amp works. No AC hum from it, no burn-outs on the circuit board or components.
Is my gut instinct correct - perhaps it's one of the electrolytic filtering electrolytic capacitors that have gone bad? None are leaking or expanded.
Any help or suggestions are much appreciated.
Thanks - Darren from Canada.
Hello Darren! Thank you for your message!
ΔιαγραφήWell, the 1st thing I would try is to check the headphones Jack! Just like the fx loop jacks, this output Jack is responsible for linking the power-amp to the on-board speaker. Rust and dust can cause distortion and low volume issues sometimes.
If the jack is Ok and you are reading zero resistance (short circuit) between R84 and one of the speaker terminals, proceed to the next step:
Check the bias voltages of the power amp (voltage readings are available in the schematics). If something is off, then the issue is definitely with the power amp section.
If all is Ok, check the speaker cone for signs of wear/tear. Also, move the cone up and down a bit with your hands. If you feel something rubbing internaly as you move the cone a bit, the speaker-coil could be damaged and needs repair/replacement.
If the speaker is Ok, I would suspect that the amp has some kind of intermodulation or crossover type distortion. This could be caused by faulty/leaky electrolytic capacitors (power supply filtering and AC coupling caps like C33) or faulty bias diodes (CR21 , CR22. CR23, CR24). There are plenty of scenarios for this type of issue but I would check the simplest first in order to avoid the "shotgun" method of changing many components without finding the root cause... My guess is that the speaker or the headphone jack are to blame.
Cheers,
Thanos
Hi Thanos. I think I figured out my problem. It has nothing to do with the amp itself, but the speaker is shot. It "works", but there's something wrong with it. It definitely has a noise coming from it when audio is played through it. I tried the amp with a different speaker, and it sounds great. I tried the Fender speaker with a different amp; sounds like crap!
ΑπάντησηΔιαγραφήLooks like I need a new speaker.
Darren
Hello Darren! I was suspecting that the speaker was to blame. Ok, so this is a classic issue. You could repair the old speaker at a speaker service center in order to get the original tone of this amp or you could simply change the speaker. There are lots of good guitar speakers out there. You need to pay attention to the dc resistance or impedance of the new speaker. I believe the stock speaker has an 8-Ohm impedance.
ΔιαγραφήCheers, Thanos