Why don't you just ask Bose what rating the fuses are? A lot of manufacturers just don't like supplying circuit diagrams, but they might tell you about the fuses.
Does the user guide say anything about the fuses?
You were on the right tracks regarding how much of the signal the tweeter receives. I don't know how much, but it's a small percentage of what the woofer gets.
Hope you find the correct answer soon.
Regards:
-Pete
HI Tech Pete,
Just a note to say thanx for the responce & add a comment regarding Bose's assistance with technicsl issues with their products.
Unfortunatekky Bose is reluctant to provide ANY technical information for their products... NEW or OLD! (other than owners manuals) If the issue requires troubleshooting down to the componant level........ dont expect any help at all! What they ARE willing to provide is a "Trade-In-Rebate" towards one of their Newer products to replace the item. They will not give you any additional information other than what is in the owners manual.... so if you expect to get a copy of the schematic YOU CAN FORGET IT! In the past I have gotton very frustrated with the help they provide............ & in future shall anticipate "Going At It Alone" (so to speak)!
Now... to answer your question "Does the user guide say anything about the fuses?" ANSWER = The user guide does mension (at least with some of the 501 Series Models, that there is an "IN LINE" fuse rated at 2amps..... However i have NEVER seen one! I believe this is an EXTRA that the consumer can purchase is they want, but does not come with the product. What Bose DOES NOT mention is.... besides this external in line fuse there is a fuse (or fmultiple fuses depending on the series) INSIDE the cabinets soldered to the crossover circuitry. Depending on the series......... there might be 1 or 2, it depends. It has also been found that in the past, Bose changed the configuration of this fusing during the Series production run.... so if you have a 501 Series II (made 4early in the production) & a 501 Series II (made late in the production)....... BOTH CIRCUITRY & COMPONANTS are different!!!!!!!!!!!!!! Personally i find this REDICULOUS! However when you take note of the changes.......... the later componants are NOT of the same quality. They are of less quality or OMITED all together! My opinion (& this is ONLY my opinion) is that Bose usually made the changes NOT to improve the quality but to CUT manufacturing cost!
It is my recommendation that when referbishing Bose 501 Series speakers, that the circuitry be checked carefully..... & when differences become apparent, ALWAYS reconfigure the pair to match. I have now restored 6 pairs of these 501's (all Series II or Series III) & when finished they sound MAGNIFICANT! Should a schematic be required for either of these two Series please let me know...... as a Complete Correct Schematic is now at my disposal...... for both Series II & Series III............ including every different configuration that has been encountered up till this time.
Again......... THANX for taking the time to respond to my problem Pete it is GREATLY APPECIATED!!!!!
(fortunatelly the issue has been resolved)
Best Regards,
Harlow
Hi Harlow,
I used to work for Hardman Radio back in the 70's. Bose was one company who's products we did not stock - I think I know why now.
As you say their policy of "Continual Improvement" is now one of reducing costs and quality. Clearly the fuses are protecting inferior drive units. Most speakers I've dealt with in the past never used fuses. However I have a pair of Goodmans HE1 which have a 2 amp fuse near the connectors - this is mentioned in the instruction manual. But for all I know the crossovers have fuses - I've never taken them apart so I don't know.
There's a lesson to be learnt here: Don't buy Bose - the company seems to be a bunch of a****oles.
Hmmm. I must have missed the solution you found. Did you measure the current until the fuse went oc?
Regards:
-TekPete
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Did you find a solution? Dunno if it's much help, but I just today picked up some 501s - Series I I think - ugly heavy brown material grilles - but with a manual! No fuses in these, but booklet recommends installing your own in-line fuse holders (!?). Specifies a BUSS AGC-3 fuse for amps under 50wpc; or a MDL-2 fuse for amps over 50 wpc. Can be placed is series with either or the two signal wires. Very strange.... Robin
Thanx Robin-Hobart, I appreciate the onput you have provide regarding my 501's. Here is some additial information regarding Bose's 501's...... 1) Make sure you know the series # of the 501's you are dealing with, each is quite different! 2) I have made schematics refering to the exact factory wiring / crossover componants / enclosure's for a few of the 501 Series..... due to the fact Bose will not provide any additional information other than the original owners manual. 3) Componants in Crossovers, Differences in Enclosures, & Speakers Themselves are apparent in each different Series #! (Example; speaker surrounds are different from series I to seies II to series III, capacitor values change in the crossover circuity, crossover circuit in series III does'nt even incorporate an inductor like the previous 2 series, resistor values change in each series crossovers, cabinet enclosures change from SEALED to BYPASS between series II and series III......... & the list keeps going!) I have a few sets of 501's now and have Restored each to near factory condition....... only using exact replacement parts when necessary, purchased direct from their own indivigual manufacturers..... which Bose purchased from. The ONLY changes that I have made to any & all of them is "I HAVE STRIPPED THE FAKE VINYL VENEER OF EACH CABINET AND RE-APPLIED GENUINE WALNUT....... nothing less than real wood!" When done retoration each of the Bose 501 Series's speakers sound GREAT! However the older Series do use better quality componants..... where componants have changed specs due to Bose's COST CUTTING + INCREASED PROFITS attitude! The Oldest Series 501's (& 901's for that matter due to I have done this with both 901 & 501 Models now) do sound BETTER & LAST LONGER........ because of the cloth speaker surrounds. Anyway, thanx again for your input Robin-Hobart! Muchly appreciated! If I can be of help to you any way regarding your Bose 501's.... let me know. I can now supply you photographs of each cabinet designed from Series I thru Series III taken during restoration, CORRECT crossover schematics for each Series with there manufacturers componant identification/part #'s. Should this information be helpfull to you "Give a little whistle.... and I'll send ya what ya need". Oh yea... by the way, the fuse which I was looking for originally when this was posted is inside the speaker (not outside/inline), soldered into the crossover circuitry..... open up the cabinet & you'll see it there..... it looks like a Light Bulb used in cars dome light, CLEAR Glass Tube, wire coming out each end....... it is a Quick Blow Fuse = Buss #2494, 2amp...... and even mounted in a Norelco #211 Holland Fuse Holder in the EARLIEST two Series 501's.................. one of the COST CUTTING achievements was to eliminate it though...... so Bose did so in the sake of making PROFITS! TYPICAL in THIS DAY & AGE! Best Regards,
Hi Mr Hyd;
Resorted to RTFM. Discovered mine are Series II - it says so in the manual. No fuses whatsoever - crossover is very simple and no fuse holders anywhere (?). Hence the manual's reference to supplying your own, external, in-line fuse. In fact, a fuse holder was the first thing I looked for as the tweeters in one cabinet are blown - suggesting an amplifier fault in one channel at some point back in history. Woofers need refoaming but I have a pair to fit (fluke!). So I need two replacement tweets - mine seem to be 8 ohms each - with the following numbers:-
104429
27928
1857534
Re the crossover - I also did a schematic - just 5 components - C1 (Left) 3 uf 250v
C2 (right) 6uf 50 VDC
R1 (Left) 3.6 ohm 15w
R2 (right) 5.1 ohm 15 w
L1 - 1 mH.
I notice the 501s are generally reviled/detested/ridiculed so I don't want to spend a lot on these - any idea where I might find 2 replacement tweeters?
Cheers.
Robin
Mr. Hyd, regarding Bose 501 Series III speakers, what's the part specification, manufacturer, etc. for the other glass bulb fuse used by the woofer...? Regards.
Hi Robin-Hobart, SORRY about the delay in responding back to ya..... I've been away on vacation for the last 2 weeks! NICE!!!!!! However now back to the grindstone. YEP YOU'VE GOT SERIES II's ! I can tell by the componants & their values which you have listed (series III's don't have an inductor on the crossover..... another cost saving for Bose Manufacturing & Profit making product downgrade for Bose Stock Holders! ) It seems to me however.... something else is wrong when you say that the tweeters are blown? If you took an ohm meter reading across that curcuit you should read 8 ohms! The two tweeters are in series with each other...., & being 4 ohms each the total resistance SHOULD BE 8 ohms. If you look closer you will find that they (the pair of tweeters) are also in series with a capacitor.... if there is NO fuse in series with the tweeters, but there is a capacitor + resistor, check the resistor for correct Ohms value with your meter (normally its fine due to the size/wattage used), should the reading be correct across resistor & 8 ohms be read directly across the two tweeters............. the problem is a blown capacitor! That 6uF Cap is NOTORIOUS for going defective! Now..... due to the different resistor values you've given me for Left & Right, sounds as though youve gotton a pair of speaker made right at the time that Bose began changing there specs...... are the woofers the same in both speakers? Do Both speakers have an inductor on there crossovers? We need More information on this end to determine exactly where in the Bose Time-Line your's were manufactured.... my guess is right at the change-over! (REGARDLESS OF THE SERIES being I, II or III.... THEY SHOULD ALL HAVE AT LEAST ONE FUSE HARD WIRED RIGHT TO THE CROSSOVER CURCUITRY!!!!! DUE TO YOU NOT BEING THE ORIGINAL OWNER OF THIS SET, LOOKS TO ME AS THOUGH THE PRVIOUS OWNER HAS REMOVED THE INTERNAL FUSE SOMETIME IN THE PAST DUE TO IT BEING BLOWN.... THAT WOULD HAVE SOLVED THERE PROBLEM & ENABLED IMMEDIATE RECOVERY OF THE OUTPUTT LOSS WHICH THEY EXPERIENCED.... HOWEVER PUT OTHER COMPONANTS SUCH AS "CAPACITORS" AT RISK IN THE FUTURE! EXACTLY WHAT I SUSPECT IS YOUR PROBLEM. In order for additional information to be relayed to you regarding correct circuitry including proper internal fusing, crossover pics, woofer pics, cabinet pics (because even the cabinets are constructed different even though they look the same.... yours having a 6uF capacitor should be a passive type enclosure), & Schematics.... it will be necessary for you to forward your e-mail address. I dont believe I can send pics, ect over this web page. Leave me your E-Mail address should additional info be required! I'll send you a schematic which will enable the Internal fusing to be re-installed..... CORRECTLY! Hope this helped ya! Again SORRY FOR THE DELAY! Best Regards
Hi Mr Hyd;
I hope you had a great holiday - it's always best to get right away.
Re these blown 501 tweets of mine - like you say, my first thought was a crossover problem (as two in one cabinet were u/s) but all my multimeter pokings about - I had both cabinets open so was able to cross-check - suggested otherwise. Finally I removed one of the suspect units and sure enough - open circuit. Definitely blown somewhere.
So, just to get a taste, I removed both bad tweets (sure enuf - both measure infinite impedance) and transplanted one good tweet to the tweet-less box. I know the impedances don't line up as per spec, but to my surprise, I reckon they sound pretty good! Potential there albeit typical Bose smear of sound-stage.
I also measured the good tweet I transplanted and it came up at just over 9 ohms.
By the way, these tweets are connected in parallel - not series (like the 901s I had). So, all in all, quite different 501 box setups to your experience.
Re the fuses - I can guarantee there ain't any, and never were any. Zilch. Nada. No evidence of prior tamperings anywhere and I am pretty sure I am the first person to violate these cabinets.
I am happy to send you some images of the instruction manual - wherein it mentions providing one's own external in-line fuses (if one thinks fit).
And pics of the crossover next time I have the woofers out if you like. I did make up a schematic of the crossover circuit - there is one inductor present in the woofer part.
Happy to swap info. My email is
[email protected]
All the best
Robin
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Not posted this as a solution incase anyone can answer with a correct fuse rating. The Manual states that these should be fitted with an external 2A Fast Blow Fuse in the +ve from the Amplifier. I'd therefore suggest fitting a 3A Fuse internally and then 2A Fuses Externally.
Thanx Andy........ appreciate the comment regarding the external 2 Amp fusing! This is stated in the documentation / owners manual provided by Bose. Unfortunatelly this 2 amp fuse is not the one which blew........ remember now, this 2 amp fuse would be sufficiant to protect the entire 501 enclosure which has one 8"woofer & two 3"tweeters + crossover. First thing is to remember is that the internal crossover filters the incoming frequencies to their respectable loads utalizing inductors and capacitors to accomplish this. Low frequencies (5 - 200 hz) are directed only towards the woofer. The tweeters on the other hand, have a capacitor in series with there coils..... which in turn STOP or filter out the lower frequencies and allow the higher frequencies (200 - 25,000 hz) to pass. Thus....... only a small percentage of total power is experienced across the coils of the two tweeters. The majority of power is dissipated by going directly to the larger woofer, the small percentage of power which is allowed to pass through the filter capacitor in the crossover is directed towards the pair of tweeters........ however must pass through an internal fuse before reaching the smaller tweeter coils. If 50% of total power was filtered in this direction & 50% of total power was dissipated by the larger woofer winding, this internal fuse would be rated @ 1amp....... my feeling is that it should be even less! Perhaps due to the tweeters being wired in parallel, which in turn splits the power load between them equally..... & also decreases the total impedance to 2 ohms........ total power drop across each would be quite low? Being in series with the woofer coil = 4 ohms....... total power drop across both tweeters would = only 33%? Should this part of the circuit be fused protected @ 33% of 2 amps? ( .666 amps ) GRRRRRR!!!!!! Not sure. Wish I had the Electrical Schematic including parts breakdown! That would solve it......... the only way to determine what this internal fuse rating REALLY is would be to remove the identical fuse from the other speaker (which is still good), hook it into a test circuit in which current flow could be monitored while gradually being increased. Fuse rating would be indicated when current reached the point of BLOWING the fuse! I just didn't want to resort to that.......... however that would resolve this issue. Why Manufacturer's won't release documentation directly related to their products which provide information that without question lengthens the life of their products service & keeps its manufactureres "Company Logo" in the public domain enabling it to be seen is CRAZY!!!!!! Its GOOD FREE MARKETING!!! MAKE SENSE to proved this type of information to anyone that askes to me... but who am I anyway?!?!?!? lololololol Thanx again " andys_elec " for your responce.... I appreciated it. It shows there are still people in this world that are willing to help others as best as they can !!!!!! Even when there isn't any monitary gain involved........... some people still try to help!!!!!! & Give it their all !!!!!!!!!!!! These type of individuals are not common in this day and age......... EXTREMELLY RARE as a matter of fact....... however they are still out there!!!!!! & are appreciated a GREAT deal. You are one of these People!!!!!!! Thank You for being out there! Hope I can return the favor one day......... I can assure you only one thing.... "I will always help anyone in need to the best of my ability till the day I die..... & enjoy a smile as reward when succesfull......... THATS ENOUGH FOR ME TO BE HAPPY!!!!!!!!!!!!! (isn't being happy everones goal in life? I think so......... don't you? KEEP SMILING AND BE HAPPY!!!!!!!!
Got your message Robin & e-Mail address............ I'll put some info/pics together asap (might take me a day) and get them off to ya. Just so you'll know the mail is from me I'll title it "Bose Info"............ keep an eye out! Hmmmmmm, you say the tweeters in yours were wired parallel? & the windings are 9 ohms impedance/resistance? GGGGGGGGGGGGG's !!!!! Something fishies going on here my friend......... tweeters should be 4 ohms & in series..... woofer should measure 6-8 ohms as well? My goodness it seems as though i'm getting more confused everytime another cabinet is opened! Well enough said for now here....... I'll be in touch via your GMAIL, with some pics.......ect. (by the way, even if there were fuses hardwired directly to the crossovers it would be VERY difficult to tell they were ever there once cut out. Both ends of the fuse are going to a point on the crossover in which multiple wires are located) Anyway...... we shall figure this out soon. TOO MANY DIFFERENCES are being experienced for my liking... thats for sure! Look forward to brain-storming this one with ya...... in te end we'll WIN!!!!!!! Chat Again Soon............ Harlow
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