Dead Fender Stage 185-replacing thermisto

kepeb · 10-29-2009, 03:16 PM

hey,
yea across the resistor r174 its like holding the probes in the air. so open i guess.

the side with audio to ground gives no reading

the side without audio reads 5.0 ohms. just thought i'd check this was right before i do that test

kepeb · 10-29-2009, 03:56 PM

AWESOME! i have sound!

i jumpered over the resistor and its got sound out.
so does that mean the coil is ok?

i just need the two resistors then.

Phostenix · 10-29-2009, 04:27 PM

Success!

Since the coil & R174 are in parallel, jumpering one also jumpers over the other, too.

I read here recently where someone's amp had that coil (most amps these days have the same coil & resistor at the output) break loose - the solder joint(s) cracked, leaving the resistor to take the current of the load and it failed. This sounded like it might be your scenario since the audio was on one side of the pair, but not on the other.

Do a visual inspection of the coil. Do you see any breaks? Is it loose at either end if you wiggle it? The only way to know for sure is to pull the board & check the other side.

Plug a guitar into the amp with R174 jumpered and play a little. Make sure it sounds normal on both channels. Test the controls & the loop, too. As long as you don't play it fully cranked, it will be OK. Do give it a couple of loud bursts, though, to make sure it can deliver some punch without doing anything strange. I just want to make sure there's nothing else going on before you order parts.

Enzo · 10-30-2009, 02:22 AM

Pull up on each end of the coil to see if its wire is broken off at one end. Also look closely at its solder. The coil is literally just a piece of wire, so it is either broken somewhere or not soldered. And replace the resistor with a good one as it needs to be there across the coil.

kepeb · 11-01-2009, 01:52 PM

well. it took a while to figure it out but the coil is broken as you suggested.
it all looked fine and the solder was ok underneath but it was cracked through a leg and i didnt see it.
can i get replacements for this?
do i need a specific type?

i was about to go ahead and get what i need from banzai music. they seem pretty good.

kepeb · 11-01-2009, 02:17 PM

http://www.banzaimusic.com/Royal-Ohm-10-ohm-1W.html

is that the right resistor also?
there are 3 or 4 types and they dont really look the same.
this is 10ohm 1watt tho.

theres the other resistors on there too. i cant see any coils tho.

kepeb · 11-02-2009, 04:29 AM

yep.
i'm stumped at coils.
i'm definirtely not sure how or why they even work.
i have found a couple that are the same value 2.5uf but they look different and the information i have found leads me to believe i have to be quite accurate in amount of turns and wiregauge or thickness here.
is this important?

RADIO RF CHOKE COIL 2.5 uH 200 MA HAM RADIO (x2 pcs.) on eBay (end time 05-Nov-09 22:15:07 GMT)

or

2 Coil Choke Inductor 2.2uh 1.8A 1H64C2201 ref 3060 on eBay (end time 18-Nov-09 14:54:48 GMT)

any final thoughts?
the rest of my bits should be on the way tomorrow

Phostenix · 11-02-2009, 03:45 PM

I wonder if you would be better off contacting a Fender dealer in your area & asking them if they can get these parts - ask them about the .22 ohm resistor, too.

I'm not sure that either of those coils would work in this application. Try checking with speaker builders/repairers, too.

kepeb · 11-02-2009, 05:28 PM

i'll try that then.
are these coil measurements pretty specific then?

Enzo · 11-03-2009, 02:26 AM

The coil of wire is just a coil of wire. The inductance is determined by the dimension of the coil, the numnber of turns, etc. But it is not critical. The coil wire is broken off at one end, probably where it goes through the board, right?

Remove the coil, take the broken end, and unwind one turn there enough to form the lead to fit back through the hole in the board. Scrape the enamel off the wire end so it will take solder. Reinstall the coil. AMp should now work.

kepeb · 11-03-2009, 10:46 AM

well,
Enzo,
Phostenix.

your help has been invaluable, educational and has given me much more confidence with this kind of thing.

it also means my fenders back up and running.
awesome guys
thanks so much

kev.

Phostenix · 11-03-2009, 03:46 PM

Were you able to get the resistors replaced, too?

kepeb · 11-03-2009, 04:26 PM

well, i have an order coming for
2 proper fender jacks for that pre out-power in section, bringing it back up to scratch.
the little resistor on the output (parallel with the coil which i now can fix too)
and a choice of matching value 20w or two smaller ones to use parallel as the power resistor replacement. i'll see which ones fit better.
and finally some heat grease for when i put the board back at the end.
sweet.
i just have to wait for it all now

kepeb · 11-03-2009, 05:22 PM

well, i'm pretty excited about the prospect of getting the fender back on its feet

i wouldnt think i will get the parts till the end of next week. TOO LONG

i might even get into one of the other ex gigging amps i have prized but is currently useless. think that deserves a new thread tho, after i look through the forum see if anyone else has already been there.

definitely better than using the time fixing xlrs.

Phostenix · 11-03-2009, 05:46 PM

It always feels great to get them working again, doesn't it?

10-29-2009, 04:27 PM	#143
Phostenix Senior Member Join Date: Jul 2009 Location: Phoenix, AZ Posts: 291	Success! Since the coil & R174 are in parallel, jumpering one also jumpers over the other, too. I read here recently where someone's amp had that coil (most amps these days have the same coil & resistor at the output) break loose - the solder joint(s) cracked, leaving the resistor to take the current of the load and it failed. This sounded like it might be your scenario since the audio was on one side of the pair, but not on the other. Do a visual inspection of the coil. Do you see any breaks? Is it loose at either end if you wiggle it? The only way to know for sure is to pull the board & check the other side. Plug a guitar into the amp with R174 jumpered and play a little. Make sure it sounds normal on both channels. Test the controls & the loop, too. As long as you don't play it fully cranked, it will be OK. Do give it a couple of loud bursts, though, to make sure it can deliver some punch without doing anything strange. I just want to make sure there's nothing else going on before you order parts. __________________ ST in Phoenix

10-30-2009, 02:22 AM	#144
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 9,271	Pull up on each end of the coil to see if its wire is broken off at one end. Also look closely at its solder. The coil is literally just a piece of wire, so it is either broken somewhere or not soldered. And replace the resistor with a good one as it needs to be there across the coil. __________________ Education is what you're left with after you have forgotten what you have learned.

11-02-2009, 03:45 PM	#148
Phostenix Senior Member Join Date: Jul 2009 Location: Phoenix, AZ Posts: 291	I wonder if you would be better off contacting a Fender dealer in your area & asking them if they can get these parts - ask them about the .22 ohm resistor, too. I'm not sure that either of those coils would work in this application. Try checking with speaker builders/repairers, too. __________________ ST in Phoenix

11-03-2009, 02:26 AM	#150
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 9,271	The coil of wire is just a coil of wire. The inductance is determined by the dimension of the coil, the numnber of turns, etc. But it is not critical. The coil wire is broken off at one end, probably where it goes through the board, right? Remove the coil, take the broken end, and unwind one turn there enough to form the lead to fit back through the hole in the board. Scrape the enamel off the wire end so it will take solder. Reinstall the coil. AMp should now work. __________________ Education is what you're left with after you have forgotten what you have learned.

11-03-2009, 03:46 PM	#152
Phostenix Senior Member Join Date: Jul 2009 Location: Phoenix, AZ Posts: 291	Were you able to get the resistors replaced, too? __________________ ST in Phoenix

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Similar Threads

10-29-2009, 03:16 PM	#141
kepeb Member Join Date: Jun 2009 Posts: 92	hey, yea across the resistor r174 its like holding the probes in the air. so open i guess. the side with audio to ground gives no reading the side without audio reads 5.0 ohms. just thought i'd check this was right before i do that test

10-29-2009, 03:56 PM	#142
kepeb Member Join Date: Jun 2009 Posts: 92	AWESOME! i have sound! i jumpered over the resistor and its got sound out. so does that mean the coil is ok? i just need the two resistors then.

11-01-2009, 01:52 PM	#145
kepeb Member Join Date: Jun 2009 Posts: 92	well. it took a while to figure it out but the coil is broken as you suggested. it all looked fine and the solder was ok underneath but it was cracked through a leg and i didnt see it. can i get replacements for this? do i need a specific type? i was about to go ahead and get what i need from banzai music. they seem pretty good.

11-01-2009, 02:17 PM	#146
kepeb Member Join Date: Jun 2009 Posts: 92	http://www.banzaimusic.com/Royal-Ohm-10-ohm-1W.html is that the right resistor also? there are 3 or 4 types and they dont really look the same. this is 10ohm 1watt tho. theres the other resistors on there too. i cant see any coils tho.

11-02-2009, 04:29 AM	#147
kepeb Member Join Date: Jun 2009 Posts: 92	yep. i'm stumped at coils. i'm definirtely not sure how or why they even work. i have found a couple that are the same value 2.5uf but they look different and the information i have found leads me to believe i have to be quite accurate in amount of turns and wiregauge or thickness here. is this important? RADIO RF CHOKE COIL 2.5 uH 200 MA HAM RADIO (x2 pcs.) on eBay (end time 05-Nov-09 22:15:07 GMT) or 2 Coil Choke Inductor 2.2uh 1.8A 1H64C2201 ref 3060 on eBay (end time 18-Nov-09 14:54:48 GMT) any final thoughts? the rest of my bits should be on the way tomorrow

11-02-2009, 05:28 PM	#149
kepeb Member Join Date: Jun 2009 Posts: 92	i'll try that then. are these coil measurements pretty specific then?

11-03-2009, 10:46 AM	#151
kepeb Member Join Date: Jun 2009 Posts: 92	well, Enzo, Phostenix. your help has been invaluable, educational and has given me much more confidence with this kind of thing. it also means my fenders back up and running. awesome guys thanks so much kev.

11-03-2009, 04:26 PM	#153
kepeb Member Join Date: Jun 2009 Posts: 92	well, i have an order coming for 2 proper fender jacks for that pre out-power in section, bringing it back up to scratch. the little resistor on the output (parallel with the coil which i now can fix too) and a choice of matching value 20w or two smaller ones to use parallel as the power resistor replacement. i'll see which ones fit better. and finally some heat grease for when i put the board back at the end. sweet. i just have to wait for it all now

11-03-2009, 05:22 PM	#154
kepeb Member Join Date: Jun 2009 Posts: 92	well, i'm pretty excited about the prospect of getting the fender back on its feet i wouldnt think i will get the parts till the end of next week. TOO LONG i might even get into one of the other ex gigging amps i have prized but is currently useless. think that deserves a new thread tho, after i look through the forum see if anyone else has already been there. definitely better than using the time fixing xlrs.

11-03-2009, 05:46 PM	#155
Phostenix Senior Member Join Date: Jul 2009 Location: Phoenix, AZ Posts: 291	It always feels great to get them working again, doesn't it? __________________ ST in Phoenix

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