Vintage Bose 800 802-E 901 Equalizer Repair & Upgrade Service

Please note: due to some health issues, I'm backlogged. Turnaround will be 21 days minimum. 

Please read through the entire listing. I take pride in the quality of my work, and the carefully selected components I use. Unlike some others, I want YOU, the customer to know up front what you'll be getting for your hard earned dollar, how long it's going to take, and what to expect when you receive your re-conditioned Equalizer. This listing is for my Basic Capacitor Replacement and Maintenance Service. I urge you reveiw and consider all of  my Exclusive Upgrade Options, which will take your Equalizer to the next level. If you decide that the additional options are beyond your budget, no worries, my Basic Service will correct the most common problems, and your Equalizer will sound as good, if not better than when it was new, due to the premium components I use, and the cleaning and other services provided. I invite you to review my Feedback, and visit my DHS Speaker Service website, and DHS Speaker Facebook  page for more details, photos, and customer reviews. Contact me directly for the address, since eBay no longer allows direct links.

Please don't be intimidated by all the upgrade options. I know they can be a bit confusing. If you have any questions please feel free to contact me here, or via my website.

Restore your Bose® 901 Series I through VI Equalizer, Bose® 800, 802-E Controllers to like new condition. Most problems associated with these Equalizers can be traced directly to aging capacitors, dirty switch contacts, dirty or worn rear connectors, and contaminated sliders (potentiometers). Symptoms may be subtle or dramatic, and can manifest themselves as a loss of signal in one or both channels, intermittent or erratic switch operation, various forms of distortion in the music signal, flat or lifeless sound, and little or no change in sound quality when adjusting the bass and treble controls. All Electrolytic Capacitors used in these Equalizers are subject to age. Some are over 40 years old now. Over time, the electrolyte dries out or leaks, the casing may begin to bulge, and in some cases may rupture. This causes capacitance values to drift, or complete failure of the components. All electronic components that contain Electrolytics when left sitting idle, unused, packed away, in an un-powered state can accelerate this condition. Although Bose® used quality General Purpose Capacitors typical for the day, no two equalizers were fitted with the same Capacitors. Each production run used whatever they had on hand. Capacitors from several different manufacturers are commonly found in the same equalizer. As with most other things, Capacitor technology has advanced dramatically in the past 30-50+ years. Electrolytic Capacitors are not like fine wine, they don't get better with age. If your equalizer is more than 12-15 years old, your Capacitors have already begun to deteriorate.

Basic Capacitor Replacement And Maintenance Service: 

My Basic service replaces all the aging, and defective Electrolytic Capacitors with Premium, Fresh Stock, Aluminum Electrolytics (I do not use "New Old Stock"). The Capacitors I use have temperature and voltage ratings equal to or higher than the originals and  are vastly superior to the General-Purpose Capacitors Bose® used originally. The power supply section will receive higher value, 1000uf, Low ESR, Long Life,  Premium,  Aluminum Electrolytic Capacitors, instead of the 470/500uf originally equipped. I've decided to make these costlier, higher value Capacitors standard for the Power Supply Section on all rebuilds. They offer much longer life, lower impedance, higher ripple current, and better filtering than the originals. This is critical for the earlier Series I through III Equalizers which have relatively simple Power Supply Sections. For the Basic service, the Audio Section will be fitted with Premium Nichicon Muse UFG Series, Aluminum Electrolytic Capacitors. I've switched to the costlier Nichicons, so that even those who just want a basic, conservative upgrade, will receive audio grade components.

Some early Series I Equalizer's rear RCA connectors were not properly grounded. This can cause intermittent signal loss and distortion. If your Equalizer does not have the improved ground connections, I'll install a dedicated copper ground lead to correct the problem at no additional cost. Some Series IV Equalizers also suffer from stress fractured solder joints on the RCA connectors. These will be re-soldered as necessary, again at no additional cost to you. Some early Series IV Equalizers and 802-E Controllers were shipped with marginal, or defective dual operating amps (please read the notes section below). 

All switches, sliders (potentiometers), and rear jacks will be cleaned and lubricated with Caig Laboratories DeoxIT® brand cleaners, lubricants and contact enhancers. Where possible, the rear connections (RCA and 1/4"), will be straightened and re-tensioned to provide better contact. The Series I & II Equalizers in particular, are known to have very dirty switch contacts, and worn RCA jacks. The rocker switches that Bose® used were open type, and subject to lubricant dry-out and contamination, and the RCA jacks were mediocre quality, typical for the day, and are easily damaged. I use only the finest Soldering/De-Soldering Materials and Techniques, including Ultra Premium Cardas Quad-Eutectic or Kester solder exclusively. After completion, all Equalizers are tested. This service is limited to fully and or partially functioning equalizers only (partially functioning means the unit at least powers up). Why choose me over some others, or Bose® Factory Service? I'm a Bose® owner, and have been for over 40 years. I've owned every Series 901 from the originals through Series VI, as well as the 800 and 802 Pro Series. I know what they're supposed to sound like, and what improvements can be made. I've personally seen very shoddy workmanship and poor quality parts from Bose® Factory Service, and Factory Authorized Service. Several customers have sent me Equalizers previously serviced by Bose®, which failed, or were deemed un-repairable. I invite you to read my feedback to see what others have said about my restoration work. Applicable Equalizers and Controllers are: 901 Series I through VI, All Series 800, 802-E. I also service some 802-C controllers, but please contact me before hand for details. Simply pack up your Equalizer and ship it to me. I'll perform all the work mentioned above, re-pack it, and ship it back to you free, via USPS Priority Flat Rate, Insured for a replacement value of $200.00. Turn-around time is usually 3-5 days, but may be much longer depending on my workload, it's "first in, first out" and does not include shipping time both ways. Note: buyer is responsible for all shipping and insurance cost associated with shipping the unit to me. 

All Upgrades and Their Respective Prices Listed Below, Are in  ADDITION to the Base  Recap and  Maintenance Service

My Exclusive Upgrades:

Neon Lamp/LED Replacement: For ALL 901 Series I through IV Equalizers, and 800 Series Equalizer/Controllers, I offer a replacement for dim, flickering or burned out neon indicator lamps. The replacement is a low output LED, available in OEM Style Amber/Orange for Series I, or Red for Series II through IV and 800 Series. If the original neon lamp holder and lens are serviceable, they will be re-used. If the lamp holder and lens are broken or missing, a new LED with an integral lens and trim will be installed. This newer, integral type is not an exact match for the original, but is close in appearance and does blend well with the equalizer's front plate. Note: aging/flickering neon lamps are a known cause of added noise in the audio signal, since they are not isolated from the rest of the power circuitry. Bose's own Factory Service frequently replaces these with LEDs when this problem occurs. The additional cost for this is $16.00.

RF Shielding: For 901 Series III and IV Equalizers. I offer heavy duty, Aluminum Foil, RF Shielding, covering the entire underside of the wood cap. The original shielding provided by Bose was minimal at best, and only covered a portion of the underside of the cap. The Series III are especially vulnerable to this. The additional cost for this is $10.00. 

New Rubber Feet: For all Series 901 Equalizers, 800, and 802-E Equalizer Controllers with missing or damaged feet. I offer Quality, Heavy Duty Rubber Feet. These are direct replacements for 901 Series I & II, and 800 Series Equalizer Controllers (the originals are 1/4" high, half-round. The new feet are 1/4" high, flat, disk type). For 901 Series III through VI, 802-E, I offer Square feet similar to originals.  The additional cost is $8.00 for 800, 901 Series I & II, and $6.00 for 802-E and 901 Series III through VI.

Replacement Treble Control Knob: For 901 Series I & II, I offer a replacement for your damaged or missing Treble knob. These are quality, solid, brushed aluminum. They are not an exact replacement, but do blend well with the front face plate. They also feature a knurled edge for easier turning. The additional cost is $7.50

Replacement Transformer & Voltage Conversion: For 901 Series I through VI, 800, and 802-E. I offer quality replacement Transformers that are robust and better than the originals. Since Bose® no longer sells parts for their equalizers, or anything else for that matter, It took me a while to find suitable, low height, quality parts, that are compatible with the entire line of Bose® Equalizers. These new Transformers are a modern design, with full EMI shielding. There are two versions. The smaller version fits Bose® 901 Series I through IV, 800, and  802-E Series, while the larger version fits the 901 Series V, VI. Pricing: 901 Series I through IV, 800 & 802-E Series, $35.00, 901 Series  V, VI $45.00. For Voltage Conversion, use in other Countries, or if your cord is defective, I stock replacement US 120 volt, and EU compatable 240 volt power cords.

Special note for Series I, II, III and 800 Series, 220-240 volt models: Most units that were shipped from the factory did not contain a true 220-240 volt transformer. Bose® used a rather unique, some would say dubious method to "convert" a 120 volt model to 240 volt. A five watt resistor was installed in the power circuitry to lower the input voltage to the transformer. You can verify this for yourself, by removing the wood cap. On Series I, II and 800 Series, the resistor is located on the front terminal strip, or attached to the power switch. On Series III, the resistor is located at the left rear of the cicuit board, behind the transformer. This scenario causes two potential problems: 1st is excessive heat, and 2nd is voltage drift. When the Equalizer is under full load conditions, the resistor gets very hot. This causes the internal cabinet temperature to rise, and may contribute to premature failure of certain components including the resistor itself. The 2nd problem is voltage drift. The active components in the Equalizer require certain minimum voltages to operate properly at all signal levels. The 5 watt resisitor's value can drift due to heat. When combined with the mediocre quality of the original transformers Bose® used, these minimum required voltages can and do drop well below that which is required for proper operation. The bottom line is: Your 220-240 volt equalizer may not be operating at peak performance, and quite possible never has. 

NEW! Regulated Power Supply Upgrade for Series I, II & III:   The early 901 Equalizers have rather simple Power Supplies, with fixed resistors, and marginal Transformers. The Amplifiers which produce the Boost Curve require specific voltages for proper, consistent operation. These fixed voltages can vary due to incoming line voltage fluctuations, and a varying load on the Equalizer depending on the incoming music signal. This Power Supply Upgrade eliminates all voltage fluctuations completely. The upgrade includes the Heavy Duty Transformer listed above, New Ultra Fast Rectifier Diodes bypassed with Ceramic Capacitors, and a New, Heavy Duty Voltage Regulator. Price for this upgrade is $60.00

Gold Plated RCA Jack Upgrade: For 901 Series I through IV. Replace all the worn, misshapened, poor quality, and poorly spaced original RCA Jacks with Premium, Gold Plated Jacks. For Series I & II, plug spacing is increased, so most premium RCA interconnect cables can be used. The original Jacks furnished on all early Bose® Equalizers were mediocre at best, and are a constant source of problems. Whether it's corrosion, elongated/misshapened internal sleeves and contacts, deteriorated solder points, poor spacing, or grounding issues, the original Jacks will fail unless treated with kid gloves. My new Jacks are made of heavy Brass or Copper Alloy, with Gold plating, and will last a lifetime with normal use, and proper care. Due to the amount of labor involved, the price is set at $80.00 for all eight, or $40.00 for the four Amplifier Connections only. If you don't plan to connect a tape deck, you don't need to replace all the Jacks.  

Tape Monitor Switch Bypass: For 901 Series I & II. Bose used poor quality, open type rocker switches for all the front Equalizer Controls. The Tape Monitor Switch is notorious for causing numerous problems, such as channel dropout, distortion, one channel weaker than the other, etc. Since very few of us actually use Tape Decks anymore I can jumper the switch internally with OFC copper wire, and install covers over the Rear RCA Tape Monitor Connectors. This will eliminate all problems associated with the Tape Monitor Switch. The modifications are completely reversible, and the outward appearance of the Equalizer will remain the same. The cost for this modification is $12.50. 

Amplifier Upgrade # 1: For all 901 Series I & II Equalizers. I can replace the old, tired Amplifiers (Transistors) with With New, Premium Fairchild  Low Noise Amplifiers. These Amplifiers do all the "heavy lifting" when creating the Boost Curve for the Equalizer. I'll also include replacing the Six Ceramic Capacitors which are in series with several of the Amplifiers with Premium Vishay Capacitors. The additional cost for replacing all 10 amplifiers and 6 Ceramic Capcitors is $24.00.

Amplifier Upgrade # 2: For 901 Series III Equalizers. I can replace all 14  old, tired Amplifiers (Transistors) with New, Premium Fairchild Low Noise Amplifiers. As with the other Equalizers, these Amps do all the "Heavy Lifting" when creating the Boost Curve for the Equalizer. The additional cost to replace all 14 Amplifiers is $26.00

Amplifier Upgrade # 3: For 901 Series IV Equalizers & 802-E controllers. As described in the notes below, The early production units were furnished with dodgy Motorola LF353 Dual Operating Amplifiers, and Bose issued a Service Bulletin addressing this. Like the Amplifiers for Series I & II, these Dual Operating Amplifiers do all the "heavy lifting" when creating the Boost Curve. I always recommend replacing these pre-emptively when rebuilding the Equalizer. These can be replaced with New, Matched, Audio Grade Amplifiers. The additional cost for replacing all four Dual Op/Amps is $12.00 if Socketed, and $25.00 if soldered in place. 

Amplifier Upgrade # 4: For 901 Series V & VI. Replaces the tired Quad and Dual Operating amplifiers with new, low noise Amps. Price for two Quad op/amps and two dual op/amps is $42.00

Voltage Regulator Replacement: For 901 Series V & VI. I'm seeing an increasing number of Series V & VI Equalizers with defective or marginal Voltage Regulators. The Voltage Regulators supply the required +15 & -15 Volts to the Quad Operating Amps. Their operation is critical since the Quad Op/Amps are the heart of the Equalizer. The Voltage Regulators are a complementary pair, and must be replaced as a pair, from the same manufacturer. A common symptom is a low frequency hum, with no music signal from either channel. The additional cost for replacing the pair is $7.50. If yours are defective or marginal, you will be notified after I inspect the unit. They can also be replaced preemptively, to prevent problems down the road.

Audio Upgrade # 1: (Elna has discontinued the Silmic II line entirely. Once my supply is gone, Premium Nichicon Muse UKZ Series will be used instead) For ALL 901 Series I Through VI Equalizers, 800, 802-E Controllers: Upgrade to Ultra-Premium, Audiophile Grade, Elna® Silmic II, High-End, Silk Fiber Aluminum Electrolytics. Regarded by many Audiophiles as the Ultimate Electrolytic Capacitor for Audio applications (with the exception of uber expensive, specialty, hand made, and oil filled capacitors). These Elna® Capacitors are equal to or better than the prized Rubycon® Black Gate® Capacitors, which are no longer in production. In addition to the exclusive Silk Fiber Electrolyte, these Elna capacitor feature Oxygen Free Copper Leads. Additional pricing varies depending on which Series Equalizer Controller you have. For 901 Series I & II, 800, 802-E, the additional cost is $10.00. For 901 Series III Through VI, the additional cost is $6.00. Note: Panasonic® FM/FC Series will still be used in the Power Section.    

Audio Upgrade # 2: For 901 Series I & II Equalizers, and 800 Series Equalizer Controllers: The input coupling and signal path capacitors can be replaced with Premium WEMA MKP Metalized Polypropylene Capacitors. Unlike the bypass/filter Electrolytic capacitors included in the basic service listed above, these capacitors are used directly in the audio signal path. In other words, the actual music signal from your pre-amp, or the pre-amp section of your receiver passes through them. The original capacitors Bose® used were good quality Mylar or Polyester, but were general purpose, dipped film (usually "Orange Drop" or encapsulated, epoxy sealed), 10% tolerance. This means that the total capacitance values between channels my differ up to 20%, and may be audible to discerning listeners. Although these film capacitors don't age like electrolytics, they do have a direct impact on the quality of the audio signal. (Note: Premium Electrolytic Output Coupling Capacitor replacement is already included in the basic re-capping price, however these two output capacitors can also be upgraded, see below.). I recapped my own Series II Equalizer with these Capacitors. I can tell you the Bass, which was rather loose and muddy from my Series II Continentals, became cleaner, tighter and more controlled, the Mid-range and Treble became crystal clear and smooth as silk. I've received similar reports from my customers who opted for this upgrade. The additional cost depends on which Series Equalizer you have and which revision it is (different Series and Revisions have different quantities which vary from 4 to 8 capacitors). The price for this upgrade is $22.00 for Series I, $16.00 for Series II, and $20.00 for 800 Series Equalizer Controllers.

Audio Upgrade # 3: For 901 Series I & II Equalizers, and 800 Series Equalizer Controllers, in addition to the Audio Upgrade # 2 listed above, the Output Coupling, Electrolytic Capacitors can also be replaced with Premium Metalized Polypropylene Capacitors. The Original Output Electrolytics have a 20% tolerance, which means the capacitance value difference between channels could be as high as 40%. These Capacitors are large, and expensive, and require special procedures during installation. The cost for these would be $28.00 in addition to the above upgrades. Once again, I modified my own Series II Equalizer with these Premium Metalized Polypropylene Capacitors, and can tell you these were the icing on the cake as far as sonic clarity is concerned. Your Series I & II Equalizer and 800 Series Equalizer Controller will perform better than when Bose first built them.

Audio Upgrade # 4: For 901 Series I & II Equalizers, and 800 Series Equalizer Controllers: There are 6 additional film capacitors in the High Frequency Audio Section, that can be replaced with Premium WIMA MKP Metalized Polypropylene Capacitors. The original capacitors Bose® used were good quality Mylar or Polyester, but were general purpose, dipped film (usually "Orange Drop" or encapsulated, epoxy sealed), 10% tolerance. This means that the total capacitance values between channels my differ up to 20%, and may be audible to discerning listeners. Although these film capacitors don't age like electrolytics, they do have a direct impact on the quality of the audio signal.  Once again, I installed these in my own Equalizer and tested them with my Series II Continentals. The Upper Midrange and Treble have never sounded better. The additional cost for this final upgrade is $14.00.

Upgrade Combination Packages: For 901 Series I & II Equalizers, and 800 Series Equalizer Controllers: I offer special combined pricing which includes all four Audio Upgrades. The performance and sonic clarity of your Equalizer and Speakers will far exceed anything Bose® ever imagined or produced. Bass response, vocals, detail, clarity and imaging are brought to a whole new level. Additional pricing depends on which Equalizer & Series you have. Please contact me before or after purchasing the Basic Recapping Service for Special Combination pricing.

Audiophile Upgrade #5: No Longer Available

Audio Upgrade # 6: For 901 Series I & II Equalizers, and 800 Series Equalizer Controllers: There are numerous NPO Ceramic Capacitors in the signal path. Many "experts" will tell you NPOs are neutral sounding, however their use in Audio Coupling Circuits can be less than stellar in my opinion. The best replacement for them is Silver Mica. Silver Mica Caps have been around for decades, but due to their high cost, manufacturers rarely use them in place of cheaper Ceramics. They are only available in the smaller values, generally under 1uf. The Series I Equalizer has eight Ceramics that can be can be changed, the Series II has six, and the 800 Series, may have six or eight depending on when it was produced. I've refitted my own Series II with the Silver Mica Caps, and the difference, especially in the upper midrange and treble was immediately apparent. It's as if a veil was lifted, and fine grained detail improved dramatically over the Ceramics. Silver Mica's are expensive compared to some other premium Capacitors. I don't normally use New Old Stock (NOS), or salvaged parts, but due to very high costs, and the fact that Silver Micas don't age, you may receive a combination of New, NOS, and in some cases salvaged parts. All Silver Micas are quality Cornell Dubilier, fully tested, and hand matched. I do not use grey market or surplus Russian Caps. For Series I, the price is $30.00, for Series II, the price is $28.00. When combined with the Ultimate Audio Upgrade # 5, the results are astounding. 

Please Note: 901 Series III through VI Equalizers, 802-E Controllers do not qualify for Audiophile Upgrades # 2, # 3, # 4, Ultimate Upgrade Package # 5, and # 6. The circuit design and components used are vastly different from the original 901 Series I & II, and 800 Series Equalizer Controllers. For these Series I can offer combined discounts on other upgrades along with Audiophile Upgrade # 1.

Please contact me directly before or after your purchase, if you're interested in any of these additional upgrades. 

Special Notes:

For 901 Series I and II Equalizers: One of the most frequent questions/complaints I receive for these early models is the spacing between the rear RCA jacks. When using modern premium interconnects, the diameter of the RCA plug's cover is, in many cases, much larger than the RCA interconnects that were available when these models were produced 35-50 years ago. When these fat or large diameter plugs hit each other, the pins go in at an angle instead of perpendicular/straight. There are two ways to address this, you can file, grind, or block sand a flat spot on the part of the plug's cover that you grasp on to when inserting or removing it, or select my RCA Jack Upgrade option listed above. By creating a flat spot on both plugs, and aligning the flats to one another, it gives you just enough clearance for the plugs to slide in correctly. Failure to do either of these, will result in the RCA jack's internal sleeves becoming misshappened, and elongated again, causing intermittent, or complete loss of signal.

For 901 Series III: Having serviced dozens of these models, I've observed the following: All Series III Equalizers have a relatively high noise floor, and are susceptible to RF and EMI interference. Although nearly identical in appearance to the Series IV, the Series III circuitry and component layout is very different. You can observe this phenomenon for yourself, by turning the gain (volume control) of your receiver or amp all the way up, with the Equalizer in the circuit, and the source connected but paused. My re-capping and maintenance service, as well as the additional RF/EMI shielding upgrades will mitigate some of this noise, and improve the overall sound, but I cannot fix a less than optimal design.  

For 901 Series IV and 802-E Equalizers: Some early production Series IV Equalizers and 802-E Controllers were furnished with lead contaminated ICs (Dual Operating Amplifier, Integrated Circuit). Bose® issued a service bulletin addressing this. These defective ICs can produce symptoms similar to the problems mentioned in the first paragraph, such as loss of signal and distortion. If it is determined that this is a contributing factor, you will be quoted separately for replacement of these four matched ICs, as an addition to the basic re-capping service. The replacement parts would be high performance, low noise operating amps, which are superior to the originals. It's also a good Idea to replace these "proactively", since these op/amps do all the "heavy lifting" with respect to the Equalizer's Boost Curve. The replacement cost is $12.00 for socketed ICs, and $25.00 if they're soldered in place. Please inspect your equalizer to determine which factory installation method was used. Contact me for details.

For All 901 Series III Through VI & 802 Original Series Speakers: If your 901s & 802s don't sound the way they used to, or are producing odd noises, there may be another problem in addition to the Equalizer: Foam Rot. Like most speaker manufactures in the 70s and 80s, Bose® began using Polyurethane Foam for their driver's surrounds. The lifespan for this type of surround was as short as 5 years, or as long as 15 years. Bose® switched to an improved foam during the Series V production, but this newer foam still only lasts about 15 to 20 years, depending on environmental conditions. I would advise anyone contemplating purchasing my Equalizer Service to inspect the drivers in your 901s or 802s. The easiest way to inspect them is to remove one of the rear V shaped grills on the 901s or the front grill on the 802s. Please note, 901 Series I, II, late production Series VI, and 802 Series II & III use treated cloth drivers, and should never need re-edging services.

This listing includes priority return shipping and insurance for USA, all 50 states, plus certain possessions/protectorates (It does  NOT include the cost for shipping your Equalizer to me). 

Note for International Shipping: I insure your Equalizer for $200.00 US, should something go wrong during the return shipping proccess. In order to do this, on the customs form, Declared Value AND Insured Value must match. If your Country applies a Duty Fee or VAT Tax, those fees will be based in the Declared Value, not the amount you paid to purchase my services. Unfortunately there's no way around this.

Important! I am NOT selling an Equalizer! This listing is for servicing YOUR equalizer, not furnishing an equalizer. Please READ the description before you buy! I've had to cancel numerous sales because buyers didn't READ the description!