Can't say I wasn't warned.

Jeff

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Lemme see now,

Lil bitty ol Silvertone, teeny 8" speaker, pretty hot active pickups in a Taylor T 5 & a Dunlop Crybaby, things get to howling pretty good for about 15 minutes, Bzzzt, snap & ominous silence.

My best amature diagnosis is something inside this little gem wasn't designed for quite this much groove. Fella at the airport when I told him I was gonna sick pedals on my new toy warned me about the speaker, leastwise I figure the speaker is the first place to look since the tubes still light up.

No problem says I to myself, I know people. I'm laughing at myself & upside is I found where the rattle was coming from, all the nuts on the speaker were looser'n a goose & spinning freely.

OK fine, where do I attach the multimeter to find out which component died. Am I looking for
milli amps or OHMS?

Thanks in advance & go slow, keepin in mind just who you're dealing with here.

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capnjuan

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All Hands On Deck!! This means you Default, Kap'n, JP.

You are reading resistance across the voice coil; it should read somewhere near 3.2 ohms. If the voice coil is broken or burned up, it will read infinite resistance, not zero; zero is what you'd get reading the resistance of a wire. We looking for an 'open' - infinite resistance - if so, the voice coil / speaker is shot. Did the fuse blow?

Do not start the amp up until you have a temp replacement speaker tied to the output transformer. Disconnect the 8" speaker; splice/lengthen the transformer output wires to another speaker; 8 ohm okay, not going to stay connected very long. With temp speaker connected, turn amp on, observe if tubes light especially the rectifier. If all the tubes light then it's just the speaker. See other post re/ Weber; these are copies of '60s Jensens; t'were me, I'd get an alnico, 5-10 hrs to break in. Remember to get a 4 ohm model.

If the fuse didn't blow and the rectifier and other tubes light with temp load on output transformer, then it's the speaker. Presence / absence of pedals shouldn't have anything to do with it.

Fingers crossed. cj
 

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Digital meters are your (and my) friend.

I take it there was no funky burning smell?
 

capnjuan

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He must be so tired from the trip or bummed out w/ the Silvertone, he's taken to drink or bed.....
 

Jeff

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capnjuan said:
He must be so tired from the trip or bummed out w/ the Silvertone, he's taken to drink or bed.....

Naa, none of the above. I had to go grocery shopping, we kind of let the fresh grocery inventory run down before the trip & Red had an appt to get a mod for her new Prius. Something called an EV switch, under light throttle it keeps the petrol fueled engine off line till 34 mph.

EV switch is slicker than a greasy doorknob, driving around in traffic on the battery, no engine noise or vibratrion of any kind, fuel consumption meter maxed at 99.9 mpg.

OK, veer back to original thread.

The fuse is fine, there was no smoke or hot 'lectic smell, I knows what hot lectric smells like, & the tubes still light up, all 3 of em.

So what I'm hearing is I need to disconnect the speaker to run the diagnostics. No sweat, I got some domestic chores to take care of tonight so I'll locate the soldering iron in the morning & pull the wires off the speaker terminals. Guess it'd be a good idea to mark the wires & the terminals first or take a darn good pic prior. May have to root around a bit to locate a spare speaker.

Digital multi meter, ey. Hmm, in my leaque, multimeters have been kind of an expendable tool. Usually when I come across a deal on a good multimeter I give it to one of my boys. I buy mine in 6 packs & fuses by the gross. I'll take a shot at locating a decent multimeter tomorrow while I scrounge for a speaker.

Thanks, if it's just the speaker I have a feeling it's not much of a loss.. The Silvertone will ride again, hopefully by sundown tomorrow. It's all good.
 

capnjuan

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10-4; eating is good, effective auto operations good, you be da man - crew is hereby standing down to 'on-call' status. The sound you hear is the bosun piping 'retreat' or whatever swabbies do when they knock off...
 

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No burning smell? All lights still doin their thing? I'm bettin' its the speaker..........
"patient considered stable, further testing underway, awaiting transplant" Any donors out there?
 

Jeff

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Brief & fruitless search for a test speaker here locally. Blank stares when asking for a 4 OHM 8" speaker ceptin at the local shop where my Reverb Rocket is waiting for the reverb tank. Tech there didn't have one but at least he knew what I was talking about.

I know Guitar Maniacs in Tacoma has prolly a dozen laying around, didn't want to drive the 50 mi round trip to get one & if it's the speaker I think I'll take CJ's advice & order a good one online.

Figure later on this eve I'll disconnect the speaker & run a signal from an old tuner thru the speaker & see if it fires up.

My lady has been very patient & understanding over my guitar & LTG madness lately & I'm feeling kind of sheepish about the
Honeydo list. Spent most of today on more mundane domestic tasks.

She'll be home soon, I got a nice fire going & supper's pretty well organized.

Day wasn't a total loss, found one of these, still in the box, for a
song & had some fund with the T 5 & JC 90 for a while. Ooh baby ya sure have to pay attn to where the T5 is facing with the gain cranked on this puppy.

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capnjuan

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Hi Jeff: for testing purposes, you can use an 8 ohm speaker, any diameter; need only be connected to the wires from the OT - any signal means bad speaker. you can splice wiring from the OT leads to the speaker in your Roland...any speaker will do provided you don't leave it on too long.

In the meantime; order a new one here: https://taweber.powweb.com/weber/ Signature Series, 8"/4ohm; not likely to find a new one anywhere else. Same speaker used by scratch builders making Fender Champs ... and on sale.
 

Jeff

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She's on the bench & the soldering iron is heating up. Be back shortly with update.

By the way CJ, there are 4 different 8" 4 Ohm speakers on the link you posted. I'm tending toward the early breakup units.
 

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OK, disconnected the speaker wires from the Silvertone, jumped them over to one of the 10" speakers on my Guild Aspen. All 3 tubes light up & I get static from the Aspen speaker, static only, not enough signal to get any sound from the T 5 plugged into the Silvertone.

No sound from the T 5 I take as not a good thing, or maybe the Silvertone doesn't put out enough to start the bigger 10" speaker.

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Next I connect the multi meter to the speaker, speaker still disconnected from power source. I hear a subtle click from the speaker when I activate the Ohm function on the multimeter. Multimeter set on RX1K sweeps to just above Zero, indicating to my mechanical mind solid continuity. Resistance analysis, for me, being something requiring further edumication.
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capnjuan

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Hi Jeff: If I understand the pics; you have tied the Aspen speaker to the taps on the 1471 speaker while the feed wires from the OT are still connected to the 1471 speaker. Since the tubes light up, I think your 1471 speaker is just plain shot. Apart from the rectifier, the speaker will age faster than any other part of the amp.

You need to take the 1471 speaker out of the loop by disconnecting the OT wires from the 1471 speaker so only the Aspen speaker is connected to the OT. The guitar and amp can drive the Aspen speaker; it may not sound very good but some bass/mid/treble is all you’re looking for. Informative stuff on speaker operation here: http://www.bcae1.com/speaker.htm PhD not necessary to understand but speakers are more complex than usually given credit for including the movement of the voice coil. Anyway, my suggestion is to not get too arm-weary trying to salvage the speaker; i.e., you could have some resistance and the speaker could be shot anyway.

Do-over w/ 1471 speaker out of the loop. When the 1471 was working correctly, were the pots clean? Did they crackle or zz when turned? If so, they need a squirt of lubricating-type clean-em-up on them. Also squirt the input jack and push/pull guitar cord a few times while solution is wet.

We standin by. cj
 

Jeff

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Thanks CJ,

Pictures must have been unclear, I disconnected the speaker from the 1471 prior to connecting the leads to the Aspen speaker. Thus my reference to the Soldering Iron heating up. I also disconnected the aspen speaker from the power source, no soldering, clip on leads.

When the 1471 was working correctly, were the pots clean? Did they crackle or zz when turned

Noteworthy, the pots were amazingly clean, no static when turned, amp was darn quiet, When she failed it was a definite sound of something lectric giving it up, zzzzt, snap & fade to silence.
I'm prfetty sure I gotta go under the bonnet so to speak.

I just finished what I consider a definitive test reference the speaker, connected a speaker output from a tuner directly to the speaker & the speaker's talking just fine, Latin FM station loud & clear. (Well, not too loud, volume on the tuner set conservative.)

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capnjuan

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Mixed blessing; if'n it'd been the speaker, we'd be done but we know something for certain now. Combining likelihood of failure with ease of fix; try the tubes. Unlike Harmony who used way less common tubes, your lineup; 12AX7/6V6/5Y3 very common. If you tech has these loose or working take-outs, mooch/buy from him, ok to put back speaker, and do one-at-a-time replacing suspect w/ known good; turn on, ok? no? repeat. If you didn't isolate one, then pull/replace all. If the 'new' tubes are good and you don't get sound, it's probably a burned resistor. Staying away from the cap issue for now; as they decline, they usually get noiser/hummier - don't normally fail castrophically - leaking electrolyte, blown fuse and such.
 

Jeff

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CJ,

Thanks again,

Ref the tubes, all along I've been thinking even a dummy like me can switch 3 tubes & likely new tubes a good idea.

I'm gonna order a new speaker, but it's nice to know I'm not fixing a part that ain't broke. A common occurrence with us shade tree mechanics.

I need to open the chassis anyway to install a 3 prong plug so this thread'll be active a while yet.

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capnjuan

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Jeff said:
Ref the tubes, all along I've been thinking even a dummy like me can switch 3 tubes & likely new tubes a good idea anyway. I'm gonna order a new speaker anyway, but it's nice to know I'm not fixing a part that ain't broke. A common occurrence with us shade tree mechanics. I need to open the chassis anyway to install a 3 prong plug so this thread'll be active a while yet.

Fix for previous boo-boo: rectifier isn't 5Y3 like I said, it's a 6X4.

10-4; fastest way to add/ensure future mileage is speaker and tubes. Your amp has a can cap; same type/model as Coastie's. Easy to find and replace but it can wait.

There are several critical, common-value resistors that might be burned; easy to find, easy to replace but; if the tubes don't do it then I'd suggest you do the can cap and resistors at the same time. Don't know about Shade Tree mechanics in the PacNW but in SoFL, Shade Tree mechanics are into opening the hood as few times as possible .... the resistors will have to be replaced at some point anyway. cj
 

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Well, benchtop has been cleared making room for amateur amp repair. Reverb Rocket relieved some of the urgency.

Probably less stressful to take it in & pay a reasonable labor charge to fix it but I already have the soldering iron out. Providing of course, the entertainment value here is enough to keep your interest.

No luck on finding loaner replacement tubes from local tech. 6X4 not available new locally. Tech's diagnosis was leaning towards a failed capacitor.

I ordered a new Weber speaker AINiCo 8 Sig ser 8sigA-4.

Started to order new tubes & Discovered tubes come from many different mfg's, & vary in quality & price. Thought I'd check in here to see what I should be looking for.

Somehow I don't think the problem is a tube, I'd just as soon have replacements anyway.

I noted many of the tube distributors also stock & sell resistors, caps & other interesting vitals. If I'm gonna take this puppy apart & start tinkering I'd just as soon replace not just the failed part but whatever else is likely to fail in the future. Maybe order the whole shebangle at one time & save a couple bucks shipping.

Thanks in advance.

Mebbe I should hot rod it some? :twisted:

Quality of the chassis is all out or proportion to the quality of the cabinet. Pretty solid feeling little panel. Lots more gizmo's than I anticipated.

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capnjuan

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Hi Jeff; yes, in for a dime, in for a dollar. For $75 in parts and $50 in tools assuming you don't already have them, you can put the amp back in as-manufactured condition, improve the sound relative to what it did before it fritzed, and put another 40 years of useful life on it. No mods; at least not until it's back in good working order. Thereafter, you can manipulate certain resistor or cap values to make changes in frequency response and tone but first things first.

If you don't have a clear schematic, I'll send you one. You can go through the schematic and make a list of all the resistors and caps, with care towards rating - wattage - and buy them at any number of reliable suppliers but, if it were me, I'd change everything in sight; I want to play the amp, not keep dragging it to the bench because something I could have replaced failed. Don't forget a 3-wire cord not less than 16awg and 3 or 4 wiring strips with not less than three terminals.

Several must haves; pencil-style soldering iron w/ dual rating ex. 22 and 45watts, small set of side-oriented wire cutters, needle-nose pliers w/ narrow needles, one or two chopsticks, dental pick w/ hook and pointed ends, two pairs of hemostats; curved and straight point, be sure to get resin, not acid, core solder. All this stuff can be had from parts guys or Radio Shack.

We can do some of this, for orientation:

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and this for detail:

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In pic above, the resistor in the center looks possibly cracked from the heat from the resistor it's nearly sitting on and maybe the one on the right; the pic is less clear there but, in any event, getting you through this is no biggie. The object in the black circle in the first pic is the multi-section can cap. There are no 3-section can caps that will directly fit. The chassis has been punched and cut for a 1" diameter cylinder but the after-market only supports 2-section / 1" caps, not 3-section / 1" caps. There is a workaround and it's mounting a wiring strip with its foot under the transformer nut; the 'missing' 3rd section, the 5uf filter cap section for the preamp, can be easily mounted there.

Finally, you need to drain the filter caps of DC. If you are ordering resistors, you'll want one something like 5-10ohms but 10watts. Touch one end of the resistor to one of the three 'hot' cap terminals and the other to the chassis; hold it there for 30 seconds or so and then measure the voltage from the cap terminal to ground; if 0, do next terminal, if not, do over til no DC voltage present. Buy extra resistors to allow for screwing up; cutting leads too short, putting in wrong place; at .25/ea, good insurance especially when replacements are only available mail order.

Can take this off board too; will consume bandwidth and bore some folks to tears. Either way, okay. cj
 
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