NO FLY LIST - RED FLAG STEREO UNITS

BRAND	MODEL	UNIT TYPE		NOTES
AKAI
AKAI	X-1800SD, X-1810SD and most of their other 'pre-1975' R2R's	Reel to Reel tape deck	Akai utilized 'pot metal' for some 'transport cams'. These are parts that are used to mechanically control all the aspects of the tape transport. As they're made from "pot metal" and are very susceptible to corrosion starting from the inside, the ultimately and commonly causes them to crack, blister and disintegrate. I've been told this is due to a high content of Zinc and is environmentally dependant. At the time of this writing, there is a place in Montana that is 3-D printing replacements for them. Other than that, if you find that your deck is no longer functioning due to this issue, you'd have to find originals from another Akai or Roberts reel tape deck that utilizes the same part. None of it is an 'easy' repair regardless. Another issue with many of the early Akai decks are that the bottom Record / Play amplifier separates from the transport, which can make the cumbersome to work on, at best.	YELLOW CAUTION to RED FLAG to NO FLY - Due to unknown nature of transport cams and PITA factor of trying to work on the separate chassis (we made an umbilical cord to help facilitate working on some of them, but that has to be made from other 'donor' Akai decks).

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 'cheeeeeese' 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 CAUTION - 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 CAUTION - Due to balance and headphone level potentiometer issue.
KENWOOD	KA-3500	Integrated Amplifier	Bottom plate is not removable, nor has any access panel, so to do anything appreciable on the 'main circuit' board (which on this unit has pretty much everything attached, ie; power supply, output / amplifier, phono pre-amp, flat-amp etc) which means that to really service any of those circuits, you need to pretty much 'remove all the guts' from the amp. Now on a more substantial unit, this level of service / disassembly may make sense, but as this is one of their 'lower' (if not the lowest' unit at the time) "that dog don't hunt"! There may be other 'lower to mid end' Kenwood units that are constructed similarly, but we just happen to have one on the bench at the time of this writing.	YELLOW CAUTION - Due to level of difficulty to service a unit of this caliber.
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	Yellow Flag to Red Flag - If the outputs in a unit are good and all seems well, then use it, and always be cautious about exercising care with speaker loads and speaker connections (which you should do with any unit). Just be aware that the output transistors on this unit are NEC 2SB617A & 2SD587A (2 ea.) TO-220 style case, and as of this writing, a part number that we had not found a source, nor a substitution.	YELLOW CAUTION - Output transistors difficult to obtain.
KENWOOD	KA-6000	Integrated Amplifier	Lots of transistors that will undoubtedly have 'black legs' ie; Hitachi 2SC458 & 2SC871.	YELLOW CAUTION - Many transistors exhibiting 'black legs' that should / will need to be replaced. Extra work / time resources.
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	FLAG SHIP RECEIVERS	The 'power transformers' can famously 'go South' on these, and that's a fairly 'terminal' issue. We've read that that is why Marantz came out with the 2600, but we don't know how accurate that information is.	RED FLAG to NO FLY - Due to no suitable replacement or practical repair for the Marantz 2500 power transformer.


BRAND	MODEL	UNIT TYPE		NOTES
MCINTOSH
McIntosh	MR-67 AND MR-71	Stereo Tuner	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-6100	Stereo Integrated Amplifier	SEE ABOVE



BRAND	MODEL	UNIT TYPE		NOTES
PIONEER

Pioneer	SA-6500-II	Integrated Amplifier	Yellow Flag to Red Flag - If the outputs in a unit are good and all seems well, then use it, and always be cautious about exercising care with speaker loads and speaker connections (which you should do with any unit). Just be aware that the output transistors on this unit are NEC 2SB616A & 2SD586 (2 ea.) TO-220 style case, and as of this writing, a part number that we had not found a source, nor a substitution.	YELLOW CAUTION - Output transistors difficult to obtain.
Pioneer	PIONEER "Multi-Play" Cassette Tape Decks such as the; Pioneer CT-M5R, CT-M6R, CT-M50R, CT-M55R, CT-WM60R, CT-WM62R, CT-M66R, CT-WM62R & CT-WM70R, CT-WM77R (and any other of those models we missed)	Cassette Tape Deck	RED FLAG to NO FLY - We've had great luck with these in the past, but for some reason, a handful we've had lately, have been massive, fruitless, 'time sinks'. Their changer mechanism is quite intricate (which one would expect in a machine that changes between 6 cassettes automatically), but unfortunately, they are quite 'touchy' to adjust and make work consistently. The last batch all had the similar symptoms. We changed belts (not easy on the 'worm gear') but following their typical service, the changer mechanisms would act erratically. The might work through 6 tapes, a half dozen times, but then randomly 'hang up' and unfortunately, would need to be manipulated internally to free up the carriage system. Sometimes they would simply go into a repeating cycle of opening and closing. Sometimes the 'left to right' tape carriage would start it's motor in reverse, and instead of traveling away from the actual 'tape transport' would try and move towards it (even though it was already locked to it in place). The motor would spin for a while until the deck would go into error ("ERR"). There is an fine adjustment for the 'left to right' tape carriage, and while that did make a difference in some instances, it was never consistent for very long. After about 30 hours of tech time into 3-4 of them, we finally threw in the towel. Like eluded to previously, we have had 2 or 3 in the past, that seemed to work fine, and we never got any complaints from, but this latest batch has "taken the wind out of our sails" for any more of these, Pioneer Multi-Play decks. If someone has definitive information that would further our progress on these, or some 'keystone' information / process that we are missing feel free to let us know. The service manual is of little use btw.	RED FLAG TO NO FLY - Just too many inconsistencies.

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 CAUTION - 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 CAUTION - 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 vacillated between simply 'Yellow Flagging' to adding 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.	YELLOW CAUTION to RED FLAG
Sansui	8080DB	Stereo Receiver	See above notes.	YELLOW CAUTION to RED FLAG
Sansui	9090	Stereo Receiver	See above notes.	YELLOW CAUTION to RED FLAG
Sansui	9090DB	Stereo Receiver	See above notes.	YELLOW CAUTION to RED FLAG
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 to NO FLY
Sansui	QRX-9001	Quadraphonic / 4-Channel / Stereo Receiver	SEE ABOVE	RED FLAG to 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	CR-2020	Stereo Receiver	'Service Bulletin' issues regarding power supply circuit board(s) and loose components / solder joints that have to be addressed.	YELLOW CAUTION - Extra work to do 'Service Bulletin' work and shoring up components and solder joints on power supply boards.
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.

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