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Purveyors of Electronic, Musical and Vintage goods from then, now and in between. 
Since 1982.

NO FLY LIST / RED FLAG STEREO UNITS



This is a listing of units that have inordinately difficult, impractical to repair / refurbish, or are just plain, "too much trouble", at least in our opinion. Your experience may be different, and you should not base a decision to purchase, sell, trade, exchange, repair, restore, refurbish or really anything on this. We built this page primarily as a 'field reference' for us to assist in making a decision to acquire a unit. We may take it down if we come up with a more practical alternative for our use. We will be adding more units as time allows. Some units may not have 'terminal' / 'No Fly' issues, but just may be beyond practical to repair / refurb / 'stereo units / models to avoid', again, 'in our opinion' (and our opinion has been known to change upon further investigation, or acquiring additional info).
Units may be designated as "
RED FLAG", "YELLOW FLAG" or "NO FLY"

 

 

The information on this page is from deduced from what we have found while servicing units. This is a listing of units that have inordinately difficult, impractical to repair / refurbish, or are just plain, "too much trouble", at least in our opinion. Your experience may be different, and you should not base a decision to purchase, sell, trade, exchange, repair, restore, refurbish or really anything on this. We built this page primarily as a 'field reference' for us to assist in making a decision to acquire a unit. We may take it down if we come up with a more practical alternative for our use. We will be adding more units as time allows. Some units may not have 'terminal' / 'No Fly' issues, but just may be beyond practical to repair / refurb, again, 'in our opinion' (and our opinion has been known to change upon further investigation, or acquiring additional info). You may have units that you feel we should have posted for various reasons, but it is a 'work in progress', and we will likely be adding units, modifying already listed info, or removing units in the future as necessary.
These are not necessarily units we have available or for sale, nor do we know who does. This information is only posted for reference purposes.

We do not do any work on 'customers' equipment here at Oak Tree Enterprises, LLC. We only restore and sell our own inventory.

 
 

We will be listing a few more units as time allows.
 

BRAND MODEL UNIT TYPE MAIN ISSUE   NOTES
BRAND MODEL UNIT TYPE     NOTES

BIC
BIC
940, 960 & 980
Turntables
Where to start?...We've restored a few, and they are overall designs that did not survive the 'test of time' very well. They are a 'nightmare' to try and restore / refurb to perfect working order, and usually can't be to any degree of dependability

NO FLY - due to too many 'cheese' factors. Just not a 'sellable' unit, at any amount of money in our opinion
 
BRAND MODEL UNIT TYPE     NOTES

BOSE
BOSE
601 SERIES II OR III
Speakers
No issues with the speakers really. They're actually one of the Bose products we find 'listenable'. The issue is with packing them for 'safe transit'. We have done it a few times, but have decided the 6 'man hours' and the amount of material required to adequately protect the top tweeters and tweeter grills is disproportionate to a speaker of their value. The 'original / Series I' version does not have any 'special' packing issues, as the sides of the cabinet come all the way to the top of the speaker, thus providing a more stable package.

RED FLAG - Could offer as a 'local pickup / delivery' or could be removed from list, if a 'practical' way of protecting the top third of the speaker is established.
 
BRAND MODEL UNIT TYPE     NOTES

dbx
dbx
dbx NX-40
dbx-II NR encoder and decoder / disc

There are 3 'cancelling' push switches located on the front of this unit. They will commonly be 'intermittent' and need to be cleaned. The issue is that they are manufactured as a 'sealed' unit, made of either nylon or plastic. You can 'drill' or 'melt' an access in the rear of the housing to inject cleaner, but the switch housing is fairly small and 'frail' relative to other 'sealed push switches', and risky to accomplish successfully. We've had luck with some, and not with others. Replacing any one of the switches 'individually' is not practical. To replace one, you would need to replace all three as a 'unit'. The rub is, you will need another 'donor / salvage' dbx NX-40 to get switches from, and they may be in the same state, thus potentially starting the whole process over.

YELLOW FLAG - Due to switch issue.
.
 
BRAND MODEL UNIT TYPE     NOTES

HAFLER
HAFLER
DH-101
PRE-AMP

Where to start?...First of all, we love Hafler gear overall, however, we've restored / refurb'd a couple of Hafler DH-101 Pre-Amps. It is an 'entry level' pre-amp, and even that's a bit of an overstatement. Firstly, the Volume attenuator does not generally reduce the volume all the way to 'zero'. Any selected and 'hot' source is always still heard. We tried a couple of modifications to no avail.
The selector switches are of a fairly 'un-desirable' type. They are not 'self cancelling', and just 'feel cheeeeesy'. However as cheeeeesy as the selector switches feel, they fall short of the 'cheeeeeeeeeeeeeesy' feeling I/O RCA jacks across the rear panel.
Lastly, there's a disgusting amount of cross-talk between ALL sources, regardless of which source is currently selected to play. We have tried replacing the internal signal path wire (which by the way is unshielded and VERY micro-phonic) with shielded cables to no avail (other than eliminating the micro-phonics).
Now there are all kinds of folks talking about modifications / up-grades to this unit, but my issue is that it seems fairly 'half-baked' out of the chute.
There may be other issues as well, but the above is enough to add to the "NO-FLY" list.
NO FLY - due to too many 'cheese' factors. Just not a 'sellable' unit once refurbished / checked out, at any amount of money in our opinion (and again, we usually love Hafler gear).
 
BRAND MODEL UNIT TYPE     NOTES

JBL 
JBL
RADIANCE MODEL SPEAKERS
STEREO SPEAKERS

They have a decorative 'bezel / beauty ring' epoxy'ed / molded into the woofer frame that needs to be removed in order to replace their surrounds. The trim ring is difficult not to destroy in the process. Too much trouble for a speaker of it's stature.
NO FLY - due to the smaller stature of this model, we don't pursue their refurb / restoration.
 
BRAND MODEL UNIT TYPE     NOTES

KENWOOD
KENWOOD
BASIC C2
Control Amplifier / Pre-Amp

While this is a fairly versatile pre-amp, that we 'still like', it does have a few 'difficult to service' issues and a couple of 'semi-permanent' defects. Firstly there's a fairly common issue with the 'balance' control pot. It's anemic / fragile in the first place, which makes it prone to 'breaking' in such a way that it will drop channels. The 'Headphone' level control utilizes the same quality / type of pot, but obviously when it goes, the only thing that doesn't work is the 'headphone' jack. We have not found a replacement. There are a couple of websites that have photo essays on doing 'micro-surgery' on them, but it's very difficult, time consuming with sketchy results. Probably the most practical way to address the issue with the balance pot is to 'jumper' across it. It can either be left in place or removed once jumpered. The same 'fix' can be utilized on the 'Headphone Level' pot, then simply use the main volume of the pre-amp to control the headphone level (like EVERY other unit does).
     Another issue is the 'Phono Capacitance' switch mechanism. It uses a flat 'ribbon' mechanism to connect the control on the front panel, to the switch nearer the rear of the main circuit board. This can have 'difficult to repair' alignment issues which cause the switch to be intermittent.
     Another issue are the set of 5 push buttons near the middle of the unit; "Subsonic", "Low", "High", "Mode" & "Output On/Off". Once the switches are cleaned, they can become 'sticky' in their motion. We found that then 'lubricating' their locking pins seems to get them back to feeling normal.
YELLOW FLAG - Due to balance and headphone level potentiometer issue..
KENWOOD
KA-5500
Integrated Amplifier

Meter Lamp (single) requires more effort than what is typically expected to replace / change. We settled on a #280 (10V / 130mA)
 
KENWOOD
KA-5700
Integrated Amplifier
The output transistors on this unit are TO-220 style case, and as of this writing, a part number that we had not found a source.
NO FLY
Kenwood
KR-2400
Stereo Receiver
Power Switch arc's, and we have not found a replacement. The possible repair is to disassemble switch (not really meant to be disassembled) and burnish the contacts, or to 'shunt' the switch across and turn unit on and off via an alternative method. Occasionally there is a version of this switch that will allow it to be 'inverted' thus connecting via un-utilized contacts on top.

NO FLY - due to the smaller stature of this model, we don't pursue the switch replacement / repair.
Kenwood
KR-2600
Stereo Receiver
See Above

NO FLY - due to the smaller stature of this model, we don't pursue the switch replacement / repair.
Kenwood
KR-3090
Stereo Receiver
See Above

NO FLY - due to the smaller stature of this model, we don't pursue the switch replacement / repair.
Kenwood
KR-3600
Stereo Receiver
See Above

NO FLY - due to the smaller stature of this model, we don't pursue the switch replacement / repair.
Kenwood
KR-4010
Stereo Receiver
See Above

NO FLY - due to the smaller stature of this model, we don't pursue the switch replacement / repair.
Kenwood
KR-4070
Stereo Receiver
See Above

NO FLY - due to the smaller stature of this model, we don't pursue the switch replacement / repair.
Kenwood
KR-5030
Stereo Receiver
See Above

NO FLY - due to the smaller stature of this model, we don't pursue the switch replacement / repair.
Kenwood
KR-6030
Stereo Receiver
See Above

RED FLAG - This unit is 'substantial' enough, that we would pursue the repair / replacement of the power switch
 
 
 
 
 
 
BRAND MODEL UNIT TYPE     NOTES

MARANTZ
 
Marantz
2500 and 2600
FLAG SHIP RECEIVERS

The 'power transformers' can famously 'go South' on these, and that's a fairly 'terminal' issue.
RED FLAG to NO FLY - Due to no suitable replacement or practical repair for the Marantz 2500 or 2600 power transformer.
           
 
BRAND MODEL UNIT TYPE     NOTES

MCINTOSH
 
McIntosh
MR-67 AND MR-71
Stereo Receiver
Difficult to pack to ensure front glass won't get broken, and it's not 'user friendly' to remove and re-install for shipment
 
McIntosh
MA-61
Stereo Receiver
SEE ABOVE
 
 
           
 
 
BRAND MODEL UNIT TYPE     NOTES

PIONEER
 



                                             
 

           
Pioneer
PIONEER PL-40, PL-41, PL-50, PL-51
Turntable

RED FLAG - There's a couple of 'Yellow / Red' Flag issues with this series of tables. You'll want the room temp to generally be above 68 degrees for the motor not to run slow. Initially the motors will run for 15 minutes to 2 hours, then start to slow down gradually to almost then run VERY slow.
NEW INFO - We've learned, however, that with 'enough' VERY thorough cleaning of the motor ie; completely disassemble the motor, clean bushings and shaft ends 3-4 times, then re-lube, they will run at colder temperatures, and will come up to speed immediately when power up for the first time during a session, and will not now slow down over time.
The other 'time consuming to rectify' issue is the 'Auto-Return' mechanism. It is a fairly 'unorthodox' design, relative to most other table mechanisms, and requires A LOT of time in disassembly, cleaning, re-lubing and re-assembly to achieve correct function.

YELLOW FLAG - Motor must be completely disassembled, clean bushings and shaft ends 3-4 times, then re-lube, then re-assemble. VERY time consuming to restore / refurbish due to difficulty to get 'clean enough' and properly lubed.
Pioneer
QX-949 / QX-949A
QUAD / Stereo Receiver

The 4 small potentiometers (also have 4 very small, round knobs on them) that surround the 'pseudo screen' have internal nylon parts that at this point are VERY brittle, and likely disintegrating internally, even though the pot / control may seem to still function. We have looked extensively for a suitable replacement for over a dozen years to no avail.
DO NOT utilize a 'cold' contact cleaner to service these as this will likely further exacerbate the 'shattering nylon guts' issue.
RED FLAG - Due to no suitable replacement for the control potentiometers previously mentioned.
Pioneer
SX-450
Stereo Receiver
Power Switch arc's, and we have not found a replacement. The possible repair is to disassemble switch (not really meant to be disassembled) and burnish the contacts, or to 'shunt' the switch across and turn unit on and off via an alternative method. Occasionally there is a version of this switch that will allow it to be 'inverted' thus connecting via un-utilized contacts on top.

NO FLY - due to the smaller stature of this model, we don't pursue the switch replacement / repair.
Pioneer
SX-550
Stereo Receiver
SEE ABOVE

NO FLY - due to the smaller stature of this model, we don't pursue the switch replacement / repair.
Pioneer
SX-1980
Stereo Receiver
SEE ABOVE

YELLOW FLAG - There's a couple of 'yellow flag' / caution issues with the SX-1980 that we're aware of. The first is the FM 'Locking circuit'. Other than it's a common issue with these, we don't have a fix, and the unit still seems to function decently if the 'lock circuit / LED' isn't working.
The larger, and common issue with these is the 'power supply' circuit board. Pioneer 'stupidly' (at least in our opinion) mounted this not only underneath the main chassis and circuits of the unit, but also 'upside down / inverted' (with all the components 'hanging' down). Heat rises, and as there's not place for it to go, it simply 'cooks' and warps the associated circuit board. This is generally a source of issues with this unit, and will almost always need to be addressed. There are replacement / upgraded circuit board sometimes available. Most folks simply rebuild theirs, but that doesn't solve the initial design issue. Another possible, yet involved solution, would be to 'relocate' the board, even including externally. I've not seen this done, but would be possible. Another solution, and one that we've recommended, is to use a fan to cool the board. One owner of a Pioneer SX-1980 put hockey pucks under the feet of the SX-1980 and utilized a 'laptop computer cooling pad' placed under the unit.


Related to the above power supply circuit board issue with the SX-1980, we compiled a list of the other Pioneer Stereo Receivers from the SX-750 thru the SX-1980 that also designed their units with the 'inverted' power supply circuit board mounted not only in the 'lower half' of the unit, but also 'upside down' / 'inverted'. We've not seen issues necessarily related to that design on other models, but it could happen, and adding 'externally located cooling' could certainly add potential 'life' to a unit that is designed that way. Here's the list ("No" means that it is not mounted in an 'inverted' fashion. "Yes" means that it the power supply board is 'inverted' and located in the 'lower half' of the unit to cause potential issues.
Pioneer
SX-750  Yes / Inverted,  
SX-780  No,  
SX-850   Yes / Inverted,
SX-880 No, 
SX-950 Yes / Inverted,
SX-980 No,  
SX-1050 No,  
SX-1080 No,  
SX-1250 Yes / Inverted,  
SX-1280 No,  
SX-1980 Yes / Inverted.
We didn’t do any models below the Pioneer SX-750. Sorry.

 

 
 
 
 
 
 
 
 
 
 
 
 
 
BRAND MODEL UNIT TYPE     NOTES

SANSUI
 
 
Sansui
707 / 707A
Stereo Receiver
RCA I/O jacks are 'conical' / tapered in shape, referring to the 'outside / gnd / shield'. I have never seen matching, 'conically' shaped RCA plugs on cables to fit them. If you try and utilize a normal RCA plug, it doesn't fit well, and generally will 'pop off' or become detached. If anyone knows a fix / way to practically address this issue, feel free to let me know.

RED FLAG TO NO FLY - Just not worth dealing with on a unit of this stature, at least from a 're-sale / customer service' issue.
Sansui
5000
Stereo Receiver

Driver Boards are the 'Red-Flag' issues on this model (Sansui 5000) is why we have added it to our 'No Fly' list.
We get an inordinate amount of requests for driver boards from 5000X's to install in 5000's. The 5000X is when they finally got the driver board design correct / reliable. They're always among the first parts to sell off of 'salvage / donor' units. They can be rebuilt, or at least have their electrolytic caps changed, if they are still functioning (not something we would normally expect to have to do to a receiver for an 'on going basis'.
RED FLAG - If the driver boards were functioning at time of restoration, then we would possibly pursue refurb on this unit.
Sansui
5000A
Stereo Receiver
SEE ABOVE

RED FLAG - If the driver boards were functioning at time of restoration, then we would possibly pursue refurb on this unit.
Sansui
5000X
Stereo Receiver
The driver boards from the Sansui 5000X seem to be the 'fixed' version, but if they are bad or missing, then finding replacements will be tough.

YELLOW CAUTION - If the driver boards were functioning at time of restoration, then we would pursue refurb on this unit.
 
Sansui
8080
Stereo Receiver

There are a couple of 'Red-Flag' issues on this model (Sansui 8080) that, with great hesitation, realizing that it's perceived desirability on the market, we have added it to our 'No Fly' list.
The first issue is their driver boards. We get an inordinate amount of requests for those. They're always among the first parts to sell off of 'salvage / donor' units. They can be rebuilt, or at least have their electrolytic caps changed, if they are still functioning (not something we would normally expect to have to do to a receiver for an 'on going basis'.

The second issue is that the 'dial illumination' lamps are being switched on and off via the same, multi-layer, wafer switch that selects the input sources. There is almost an Amp of current going thru a switch that was probably designed for 'pre-amp' level audio signals. It may have originally been spec'd for that kind of current, but 40 years later, it has not generally held up well (relative to other gear on the market). Unfortunately it is not simply a 'contact cleaner fix'. Arc-ing has taken place and the contacts must have all their surfaces physically 'burnished'. This involves removing the switch, and dismantling it down to the 'wafers and wipers', which  was not something that the switch was designed with in mind. It generally takes about 4-6 hours to do that operation. While we generally expect to tie up 6-12 hours in a receivers restoration / refurb, to tie up that amount of time on one aspect on a recurrent basis is not practical. In other words, "that dog don't hunt!". There is another angle to address the dial lamp issue and that is to completely bypass the switch, and simply have the dial lamps on all the time, ie; even when a 'non-tuner' function is selected, but it takes the 'know how' / technician capabilities to do that.
The third issues is similar to the second. Any 'rotary / wafer' switch will have an inordinate amount of 'intermittency' due to their 'open wafer' design, and will require typically way more than normal cleaning, and again in some instances, need to be removed, disassembled, and burnished to function reliably.
If anyone has any proven and practical hint's around the above issues, we would love to take this series of models off our No Fly list.
RED FLAG / NO FLY
Sansui
8080DB
Stereo Receiver
See above notes.
RED FLAG / NO FLY
Sansui
9090
Stereo Receiver
See above notes.
RED FLAG / NO FLY
Sansui
9090DB
Stereo Receiver
See above notes.
RED FLAG / NO FLY
Sansui
QRX-8001
Quadraphonic / 4-Channel / Stereo Receiver
Has potentially SERIOUS issues with the 'double power' mode and it's quad phono boards that are VERY difficult to address, unless you are ready to invest a lot of resources into it.
RED FLAG / NO FLY
Sansui
QRX-9001
Quadraphonic / 4-Channel / Stereo Receiver
SEE ABOVE
RED FLAG / NO FLY
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
BRAND MODEL UNIT TYPE     NOTES

SONY
 
 
SONY
TC-560, TC-560D, TC-560DA
Reel to Reel

No particular 'Red-Flag' issues, but transport is difficult to 're-install'. You need about a dozen 'small hands' all at once to 'hold' and lineup multiple parts all at the same time. 'Do-able', but a 'PITA'! Also, utilizes 5-6 belts, one of which is a bit more difficult to obtain in 'correct' dimensions. Not impossible as of this writing, just usually a 'special order' and size needs to be verified by vendor for accuracy.
YELLOW CAUTION TO RED FLAG - Difficult to work on transport.
 
 
 
 
 
 
BRAND MODEL UNIT TYPE     NOTES

TEAC
TEAC
X-7, X-7R, X-700 and maybe others.
Reel to Reel


No motor tension adjustment for 'back tension'.  Face must be removed to do almost anything. Very difficult to access most assemblies.

 
YELLOW CAUTION - Difficult to address the afore mentioned service operations.
 
 
 
 
 
 
 
BRAND MODEL UNIT TYPE     NOTES

YAMAHA 
YAMAHA
R-700
Stereo Receiver
STK chip issues and 'voltage amplifier' chip issues as in not available. No 'manual' tuning capability on tuner.

NO FLY - Too many bad experiences with this one
YAMAHA
R-900
Stereo Receiver
STK chip issues and 'voltage amplifier' chip issues as in not available.

NO FLY - Too many bad experiences with this one
 
 
 
 
 
 

We will be listing a few more units as time allows.


 _____________________________________________________________________________________


Again, we do not do any work on 'customers' equipment here at Oak Tree Enterprises, LLC. We only restore and sell our own inventory.

 

 


 

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